day11-MySQL數據操做索引備份觸發器
第1章 上節課複習
1、數據庫管理軟件 本質就是套接字 2、基本概念 數據庫服務器：運行數據庫管理軟件的計算機 數據庫管理軟件：MySQL，Oracle，DB2，SQL SERVER 庫：文件夾 表：文件 記錄：1，egon，19，male，oldboy 3、基本的SQL語句 文件夾（庫） 增 create database db1 charset utf8; 改 alter database db1 charset gbk; 查 select database(); show databases; show create database db1; 刪 drop database db1; 文件（表） use db1; # 切換文件夾 增 create table t1(id int,name char(16))engine=innodb; 改 alter table t1 add age int; alter table t1 drop age; alter table t1 modify name char(10); alter table t1 change name NAME char(10); 查 show tables; show create table t1; desc t1; 刪 drop table t1; 文件的內容（記錄） 增 insert into t1(id,name) values(...),(...),(...); 改 update t1 set name='EGON' where name='egon'; 查 select id,name from t1; 刪 delete from t1 where id > 3; truncate t1; 4、數據類型 數值類型 整型： int create table t1(id int unsigned) 強調：對於整型類型寬度指的是顯示寬度 浮點型： float(255,30) double(255,30) decimal(65,30) 區別：精度依次增高 日期類型： date：1990-01-03 time：11:11:11 datetime（timestamp）：1990-01-03 11:11:11 year：1990 字符類型(寬度指的是字符的寬度) char：定長 egon |alex |wxx | varchar：變長 1bytes+egon|1bytes+alex|1bytes+wxx| create table t2(x char(4),y varchar(4)); insert into t2 values('',''); 補充SQL_MODE: set sql_mode='strict_trans_tables'; 5、枚舉類型 單選：enum(1,2,3) 多選：set(1,2,3)
第2章 MySQL之完整性約束
2.1 介紹
約束條件與數據類型的寬度同樣，都是可選參數html
做用：用於保證數據的完整性和一致性java
2.1.1 分類
主要分爲：python
PRIMARY KEY (PK) 標識該字段爲該表的主鍵，能夠惟一的標識記錄
FOREIGN KEY (FK) 標識該字段爲該表的外鍵
NOT NULL 標識該字段不能爲空
UNIQUE KEY (UK) 標識該字段的值是惟一的
AUTO_INCREMENT 標識該字段的值自動增加（整數類型，並且爲主鍵）
DEFAULT 爲該字段設置默認值
UNSIGNED 無符號
ZEROFILL 使用0填充
####ZEROFILL的使用效果 mysql> use db2 Database changed mysql> create table t3(id int zerofill); Query OK, 0 rows affected (1.74 sec) mysql> insert into t3 values(1); Query OK, 1 row affected (0.30 sec) mysql> select * from t3; +------------+ | id | +------------+ | 0000000001 | +------------+ 1 row in set (0.00 sec) mysql>
2.1.2 說明
1. 是否容許爲空，默認NULL，可設置NOT NULL，字段不容許爲空，必須賦值mysql
2. 字段是否有默認值，缺省的默認值是NULL，若是插入記錄時不給字段賦值，此字段使用默認值linux
sex enum('male','female') not null default 'male'nginx
age int unsigned NOT NULL default 20 必須爲正值（無符號） 不容許爲空 默認是20程序員
3. 是不是keyweb
主鍵 primary key正則表達式
外鍵 foreign key算法
索引 (index,unique...)
2.2 not null,default
是否可空，null表示空，非字符串
not null - 不可空
null - 可空
默認值，建立列時能夠指定默認值，當插入數據時若是未主動設置，則自動添加默認值
create table tb1(
nid int not null defalut 2,
num int not null
)
2.2.1 課堂演示
create table t4(x char(4) not null); create table user(id int,name char(16),sex enum('male','female') not null default 'male'); mysql> desc user; +-------+-----------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-----------------------+------+-----+---------+-------+ | id | int(11) | YES | | NULL | | | name | char(16) | YES | | NULL | | | sex | enum('male','female') | NO | | male | | +-------+-----------------------+------+-----+---------+-------+ 3 rows in set (0.00 sec) mysql> select * from user; Empty set (0.00 sec) mysql> insert into user(id,name) values(1,'egon'); Query OK, 1 row affected (1.68 sec) mysql> select * from user; +------+------+------+ | id | name | sex | +------+------+------+ | 1 | egon | male | +------+------+------+ 1 row in set (0.00 sec)
2.2.2 驗證
==================not null==================== mysql> create table t1(id int); #id字段默承認以插入空 mysql> desc t1; +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | id | int(11) | YES | | NULL | | +-------+---------+------+-----+---------+-------+ mysql> insert into t1 values(); #能夠插入空 mysql> create table t2(id int not null); #設置字段id不爲空 mysql> desc t2; +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | id | int(11) | NO | | NULL | | +-------+---------+------+-----+---------+-------+ mysql> insert into t2 values(); #不能插入空 ERROR 1364 (HY000): Field 'id' doesn't have a default value ==================default==================== #設置id字段有默認值後，則不管id字段是null仍是not null，均可以插入空，插入空默認填入default指定的默認值 mysql> create table t3(id int default 1); mysql> alter table t3 modify id int not null default 1; ==================綜合練習==================== mysql> create table student( -> name varchar(20) not null, -> age int(3) unsigned not null default 18, -> sex enum('male','female') default 'male', -> hobby set('play','study','read','music') default 'play,music' -> ); mysql> desc student; +-------+------------------------------------+------+-----+------------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+------------------------------------+------+-----+------------+-------+ | name | varchar(20) | NO | | NULL | | | age | int(3) unsigned | NO | | 18 | | | sex | enum('male','female') | YES | | male | | | hobby | set('play','study','read','music') | YES | | play,music | | +-------+------------------------------------+------+-----+------------+-------+ mysql> insert into student(name) values('egon'); mysql> select * from student; +------+-----+------+------------+ | name | age | sex | hobby | +------+-----+------+------------+ | egon | 18 | male | play,music | +------+-----+------+------------+
2.3 primary key
2.3.1 primary key字段介紹
從約束角度看primary key字段的值不爲空且惟一，那咱們直接使用not null+unique不就能夠了嗎，要它幹什麼？
主鍵primary key是innodb存儲引擎組織數據的依據，innodb稱之爲索引組織表，一張表中必須有且只有一個主鍵。
一個表中能夠：
單列作主鍵
多列作主鍵（複合主鍵）
============單列作主鍵=============== #方法一：not null+unique create table department1( id int not null unique, #主鍵 name varchar(20) not null unique, comment varchar(100) ); mysql> desc department1; +---------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+--------------+------+-----+---------+-------+ | id | int(11) | NO | PRI | NULL | | | name | varchar(20) | NO | UNI | NULL | | | comment | varchar(100) | YES | | NULL | | +---------+--------------+------+-----+---------+-------+ rows in set (0.01 sec) #方法二：在某一個字段後用primary key create table department2( id int primary key, #主鍵 name varchar(20), comment varchar(100) ); mysql> desc department2; +---------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+--------------+------+-----+---------+-------+ | id | int(11) | NO | PRI | NULL | | | name | varchar(20) | YES | | NULL | | | comment | varchar(100) | YES | | NULL | | +---------+--------------+------+-----+---------+-------+ rows in set (0.00 sec) #方法三：在全部字段後單獨定義primary key create table department3( id int, name varchar(20), comment varchar(100), constraint pk_name primary key(id); #建立主鍵併爲其命名pk_name mysql> desc department3; +---------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +---------+--------------+------+-----+---------+-------+ | id | int(11) | NO | PRI | NULL | | | name | varchar(20) | YES | | NULL | | | comment | varchar(100) | YES | | NULL | | +---------+--------------+------+-----+---------+-------+ rows in set (0.01 sec)
==================多列作主鍵================ create table service( ip varchar(15), port char(5), service_name varchar(10) not null, primary key(ip,port) ); mysql> desc service; +--------------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------+-------------+------+-----+---------+-------+ | ip | varchar(15) | NO | PRI | NULL | | | port | char(5) | NO | PRI | NULL | | | service_name | varchar(10) | NO | | NULL | | +--------------+-------------+------+-----+---------+-------+ 3 rows in set (0.00 sec) mysql> insert into service values -> ('172.16.45.10','3306','mysqld'), -> ('172.16.45.11','3306','mariadb') -> ; Query OK, 2 rows affected (0.00 sec) Records: 2 Duplicates: 0 Warnings: 0 mysql> insert into service values ('172.16.45.10','3306','nginx'); ERROR 1062 (23000): Duplicate entry '172.16.45.10-3306' for key 'PRIMARY'
2.3.2 課堂講解
約束字段不爲空而且惟一 依據：主鍵是innodb的表組織數據的依據 注意：一張表中必須有且只能有一個主鍵 create table t5( id int primary key auto_increment, name char(20) ); insert into t5(name) values('egon'),('alex'); select name from t5 where id = 1000; 瞭解：聯合主鍵 create table t6( id int, name char(20), primary key(id,name) );
2.4 unique key
2.4.1 設置惟一約束 UNIQUE
============設置惟一約束 UNIQUE=============== 方法一： create table department1( id int, name varchar(20) unique, comment varchar(100) ); 方法二： create table department2( id int, name varchar(20), comment varchar(100), constraint uk_name unique(name) ); mysql> insert into department1 values(1,'IT','技術'); Query OK, 1 row affected (0.00 sec) mysql> insert into department1 values(1,'IT','技術'); ERROR 1062 (23000): Duplicate entry 'IT' for key 'name'
2.4.2 not null+unique的化學反應
mysql> create table t1(id int not null unique); Query OK, 0 rows affected (0.02 sec) mysql> desc t1; +-------+---------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+---------+------+-----+---------+-------+ | id | int(11) | NO | PRI | NULL | | +-------+---------+------+-----+---------+-------+ row in set (0.00 sec)
2.4.3 聯合惟一
create table service( id int primary key auto_increment, name varchar(20), host varchar(15) not null, port int not null, unique(host,port) #聯合惟一 ); mysql> insert into service values -> (1,'nginx','192.168.0.10',80), -> (2,'haproxy','192.168.0.20',80), -> (3,'mysql','192.168.0.30',3306) -> ; Query OK, 3 rows affected (0.01 sec) Records: 3 Duplicates: 0 Warnings: 0 mysql> insert into service(name,host,port) values('nginx','192.168.0.10',80); ERROR 1062 (23000): Duplicate entry '192.168.0.10-80' for key 'host'
2.4.4 課堂講解
create table service( id int primary key auto_increment, name char(20) unique ); not null+unique:會在沒有指定主鍵的狀況下被識別爲主鍵 create table service1( id int, name char(20) not null unique ); create table service2( id int primary key auto_increment, name char(20) unique, ip char(15), port int, unique(ip,port) ); insert into service2(name,ip,port) values ('nginx','192.168.1.10',80), ('haproxy','192.168.1.10',8080), ('mysql','192.168.1.10',3306); insert into service2(name,ip,port) values ('nginx1','192.168.1.10',80);
2.5 auto_increment
約束字段爲自動增加，被約束的字段必須同時被key約束
2.5.1 auto_increment使用實例
#不指定id，則自動增加 create table student( id int primary key auto_increment, name varchar(20), sex enum('male','female') default 'male' ); mysql> desc student; +-------+-----------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +-------+-----------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(20) | YES | | NULL | | | sex | enum('male','female') | YES | | male | | +-------+-----------------------+------+-----+---------+----------------+ mysql> insert into student(name) values -> ('egon'), -> ('alex') -> ; mysql> select * from student; +----+------+------+ | id | name | sex | +----+------+------+ | 1 | egon | male | | 2 | alex | male | +----+------+------+ #也能夠指定id mysql> insert into student values(4,'asb','female'); Query OK, 1 row affected (0.00 sec) mysql> insert into student values(7,'wsb','female'); Query OK, 1 row affected (0.00 sec) mysql> select * from student; +----+------+--------+ | id | name | sex | +----+------+--------+ | 1 | egon | male | | 2 | alex | male | | 4 | asb | female | | 7 | wsb | female | +----+------+--------+ #對於自增的字段，在用delete刪除後，再插入值，該字段仍按照刪除前的位置繼續增加 mysql> delete from student; Query OK, 4 rows affected (0.00 sec) mysql> select * from student; Empty set (0.00 sec) mysql> insert into student(name) values('ysb'); mysql> select * from student; +----+------+------+ | id | name | sex | +----+------+------+ | 8 | ysb | male | +----+------+------+ #應該用truncate清空表，比起delete一條一條地刪除記錄，truncate是直接清空表，在刪除大表時用它 mysql> truncate student; Query OK, 0 rows affected (0.01 sec) mysql> insert into student(name) values('egon'); Query OK, 1 row affected (0.01 sec) mysql> select * from student; +----+------+------+ | id | name | sex | +----+------+------+ | 1 | egon | male | +----+------+------+ row in set (0.00 sec)
2.5.2 瞭解知識
######步長:auto_increment_increment,起始偏移量:auto_increment_offset########### #在建立完表後，修改自增字段的起始值 mysql> create table student( -> id int primary key auto_increment, -> name varchar(20), -> sex enum('male','female') default 'male' -> ); mysql> alter table student auto_increment=3; mysql> show create table student; ....... ENGINE=InnoDB AUTO_INCREMENT=3 DEFAULT CHARSET=utf8 mysql> insert into student(name) values('egon'); Query OK, 1 row affected (0.01 sec) mysql> select * from student; +----+------+------+ | id | name | sex | +----+------+------+ | 3 | egon | male | +----+------+------+ row in set (0.00 sec) mysql> show create table student; ....... ENGINE=InnoDB AUTO_INCREMENT=4 DEFAULT CHARSET=utf8 #也能夠建立表時指定auto_increment的初始值，注意初始值的設置爲表選項，應該放到括號外 create table student( id int primary key auto_increment, name varchar(20), sex enum('male','female') default 'male' )auto_increment=3; #設置步長 sqlserver：自增步長 基於表級別 create table t1（ id int。。。 ）engine=innodb,auto_increment=2 步長=2 default charset=utf8 mysql自增的步長： show session variables like 'auto_inc%'; #基於會話級別 set session auth_increment_increment=2 #修改會話級別的步長 #基於全局級別的 set global auth_increment_increment=2 #修改全局級別的步長（全部會話都生效） #！！！注意了注意了注意了！！！ If the value of auto_increment_offset is greater than that of auto_increment_increment, the value of auto_increment_offset is ignored. 翻譯：若是auto_increment_offset的值大於auto_increment_increment的值，則auto_increment_offset的值會被忽略 ，這至關於第一步步子就邁大了，扯着了蛋 好比：設置auto_increment_offset=3，auto_increment_increment=2 mysql> set global auto_increment_increment=5; Query OK, 0 rows affected (0.00 sec) mysql> set global auto_increment_offset=3; Query OK, 0 rows affected (0.00 sec) mysql> show variables like 'auto_incre%'; #須要退出從新登陸 +--------------------------+-------+ | Variable_name | Value | +--------------------------+-------+ | auto_increment_increment | 1 | | auto_increment_offset | 1 | +--------------------------+-------+ create table student( id int primary key auto_increment, name varchar(20), sex enum('male','female') default 'male' ); mysql> insert into student(name) values('egon1'),('egon2'),('egon3'); mysql> select * from student; +----+-------+------+ | id | name | sex | +----+-------+------+ | 3 | egon1 | male | | 8 | egon2 | male | | 13 | egon3 | male | +----+-------+------+
2.5.3 課堂講解
show variables like '%auto%'; # 結果 auto_increment_increment | 1 # 步長 auto_increment_offset | 1 # 起始位置 #強調：起始位置的值必須<=步長 set global auto_increment_increment=5; set global auto_increment_offset=3; create table t7(id int unique auto_increment); insert into t7 values(); set global auto_increment_increment=1; set global auto_increment_offset=1;
2.6 foregn key
2.6.1 快速理解foreign key
員工信息表有三個字段：工號 姓名 部門
公司有3個部門，可是有1個億的員工，那意味着部門這個字段須要重複存儲，部門名字越長，越浪費
解決方法：
咱們徹底能夠定義一個部門表
而後讓員工信息表關聯該表，如何關聯，即foreign key
#############################示範######################### #表類型必須是innodb存儲引擎，且被關聯的字段，即references指定的另一個表的字段，必須保證惟一 create table department( id int primary key, name varchar(20) not null )engine=innodb; #dpt_id外鍵，關聯父表（department主鍵id），同步更新，同步刪除 create table employee( id int primary key, name varchar(20) not null, dpt_id int, constraint fk_name foreign key(dpt_id) references department(id) on delete cascade on update cascade )engine=innodb; #先往父表department中插入記錄 insert into department values (1,'歐德博愛技術有限事業部'), (2,'艾利克斯人力資源部'), (3,'銷售部'); #再往子表employee中插入記錄 insert into employee values (1,'egon',1), (2,'alex1',2), (3,'alex2',2), (4,'alex3',2), (5,'李坦克',3), (6,'劉飛機',3), (7,'張火箭',3), (8,'林子彈',3), (9,'加特林',3) ; #刪父表department，子表employee中對應的記錄跟着刪 mysql> delete from department where id=3; mysql> select * from employee; +----+-------+--------+ | id | name | dpt_id | +----+-------+--------+ | 1 | egon | 1 | | 2 | alex1 | 2 | | 3 | alex2 | 2 | | 4 | alex3 | 2 | +----+-------+--------+ #更新父表department，子表employee中對應的記錄跟着改 mysql> update department set id=22222 where id=2; mysql> select * from employee; +----+-------+--------+ | id | name | dpt_id | +----+-------+--------+ | 1 | egon | 1 | | 3 | alex2 | 22222 | | 4 | alex3 | 22222 | | 5 | alex1 | 22222 | +----+-------+--------+
2.6.2 如何找出兩張表之間的關係
分析步驟： #一、先站在左表的角度去找 是否左表的多條記錄能夠對應右表的一條記錄，若是是，則證實左表的一個字段foreign key 右表一個字段（一般是id） #二、再站在右表的角度去找 是否右表的多條記錄能夠對應左表的一條記錄，若是是，則證實右表的一個字段foreign key 左表一個字段（一般是id） #三、總結： #多對一： 若是隻有步驟1成立，則是左表多對一右表 若是隻有步驟2成立，則是右表多對一左表 #多對多 若是步驟1和2同時成立，則證實這兩張表時一個雙向的多對一，即多對多,須要定義一個這兩張表的關係表來專門存放兩者的關係 #一對一: 若是1和2都不成立，而是左表的一條記錄惟一對應右表的一條記錄，反之亦然。這種狀況很簡單，就是在左表foreign key右表的基礎上，將左表的外鍵字段設置成unique便可
2.6.3 創建表之間的關係
#一對多或稱爲多對一
三張表：出版社，做者信息，書
一對多（或多對一）：一個出版社能夠出版多本書
關聯方式：foreign key
=====================多對一===================== create table press( id int primary key auto_increment, name varchar(20) ); create table book( id int primary key auto_increment, name varchar(20), press_id int not null, foreign key(press_id) references press(id) on delete cascade on update cascade ); insert into press(name) values ('北京工業地雷出版社'), ('人民音樂很差聽出版社'), ('知識產權沒有用出版社') ; insert into book(name,press_id) values ('九陽神功',1), ('九陰真經',2), ('九陰白骨爪',2), ('獨孤九劍',3), ('降龍十巴掌',2), ('葵花寶典',3);
##################其餘例子##################### 一夫多妻制 #妻子表的丈夫id外鍵到丈夫表的id
#多對多
三張表：出版社，做者信息，書
多對多：一個做者能夠寫多本書，一本書也能夠有多個做者，雙向的一對多，即多對多
關聯方式：foreign key+一張新的表
=====================多對多===================== create table author( id int primary key auto_increment, name varchar(20) ); #這張表就存放做者表與書表的關係，即查詢兩者的關係查這表就能夠了 create table author2book( id int not null unique auto_increment, author_id int not null, book_id int not null, constraint fk_author foreign key(author_id) references author(id) on delete cascade on update cascade, constraint fk_book foreign key(book_id) references book(id) on delete cascade on update cascade, primary key(author_id,book_id) ); #插入四個做者，id依次排開 insert into author(name) values('egon'),('alex'),('yuanhao'),('wpq'); #每一個做者與本身的表明做以下 egon: 九陽神功 九陰真經 九陰白骨爪 獨孤九劍 降龍十巴掌 葵花寶典 alex: 九陽神功 葵花寶典 yuanhao: 獨孤九劍 降龍十巴掌 葵花寶典 wpq: 九陽神功 insert into author2book(author_id,book_id) values (1,1), (1,2), (1,3), (1,4), (1,5), (1,6), (2,1), (2,6), (3,4), (3,5), (3,6), (4,1) ;
#######################其餘例子####################### 單張表：用戶表+相親關係表，至關於：用戶表+相親關係表+用戶表 多張表：用戶表+用戶與主機關係表+主機表 中間那一張存放關係的表，對外關聯的字段能夠聯合惟一
#一對一
兩張表：學生表和客戶表
一對一：一個學生是一個客戶，一個客戶有可能變成一個學校，即一對一的關係
關聯方式：foreign key+unique
#必定是student來foreign key表customer，這樣就保證了： #1 學生必定是一個客戶， #2 客戶不必定是學生，但有可能成爲一個學生 create table customer( id int primary key auto_increment, name varchar(20) not null, qq varchar(10) not null, phone char(16) not null ); create table student( id int primary key auto_increment, class_name varchar(20) not null, customer_id int unique, #該字段必定要是惟一的 foreign key(customer_id) references customer(id) #外鍵的字段必定要保證unique on delete cascade on update cascade ); #增長客戶 insert into customer(name,qq,phone) values ('李飛機','31811231',13811341220), ('王大炮','123123123',15213146809), ('守榴彈','283818181',1867141331), ('吳坦克','283818181',1851143312), ('贏火箭','888818181',1861243314), ('戰地雷','112312312',18811431230) ; #增長學生 insert into student(class_name,customer_id) values ('脫產3班',3), ('週末19期',4), ('週末19期',5) ;
#####################其餘例子################## 例一：一個用戶只有一個博客 用戶表： id name egon alex wupeiqi 博客表 fk+unique id url name_id xxxx 1 yyyy 3 zzz 2 例二：一個管理員惟一對應一個用戶 用戶表： id user password egon xxxx alex yyyy 管理員表： fk+unique id user_id password 1 xxxxx 2 yyyyy
2.6.4 課堂講解
建立表： 1、先建立被關聯的表：部門表 #強調：被關聯的字段必須惟一 create table dep( id int primary key auto_increment, name char(10) ); 2、再建立關聯表：員工表 create table emp( id int primary key auto_increment, name char(16), age int, dep_id int, foreign key(dep_id) references dep(id) on delete cascade on update cascade ); 插入記錄時： #一、先往被關聯表插入：部門表 insert into dep(name) values ('外交部'), ('技術哈哈部'), ('銷售部'); #二、再往關聯表插入：員工表 insert into emp(name,age,dep_id) values ('egon',19,1), ('alex',74,2), ('wxx',38,2), ('yxx',22,3); #錯誤操做 insert into emp(name,age,dep_id) values ('lhf',29,4); delete from dep where id=2; delete from emp where dep_id=2;
2.7 練習
練習：帳號信息表，用戶組，主機表，主機組
#用戶表 create table user( id int not null unique auto_increment, username varchar(20) not null, password varchar(50) not null, primary key(username,password) ); insert into user(username,password) values ('root','123'), ('egon','456'), ('alex','alex3714') ; #用戶組表 create table usergroup( id int primary key auto_increment, groupname varchar(20) not null unique ); insert into usergroup(groupname) values ('IT'), ('Sale'), ('Finance'), ('boss') ; #主機表 create table host( id int primary key auto_increment, ip char(15) not null unique default '127.0.0.1' ); insert into host(ip) values ('172.16.45.2'), ('172.16.31.10'), ('172.16.45.3'), ('172.16.31.11'), ('172.10.45.3'), ('172.10.45.4'), ('172.10.45.5'), ('192.168.1.20'), ('192.168.1.21'), ('192.168.1.22'), ('192.168.2.23'), ('192.168.2.223'), ('192.168.2.24'), ('192.168.3.22'), ('192.168.3.23'), ('192.168.3.24') ; #業務線表 create table business( id int primary key auto_increment, business varchar(20) not null unique ); insert into business(business) values ('輕鬆貸'), ('隨便花'), ('大富翁'), ('窮一輩子') ; #建關係：user與usergroup create table user2usergroup( id int not null unique auto_increment, user_id int not null, group_id int not null, primary key(user_id,group_id), foreign key(user_id) references user(id), foreign key(group_id) references usergroup(id) ); insert into user2usergroup(user_id,group_id) values (1,1), (1,2), (1,3), (1,4), (2,3), (2,4), (3,4) ; #建關係：host與business create table host2business( id int not null unique auto_increment, host_id int not null, business_id int not null, primary key(host_id,business_id), foreign key(host_id) references host(id), foreign key(business_id) references business(id) ); insert into host2business(host_id,business_id) values (1,1), (1,2), (1,3), (2,2), (2,3), (3,4) ; #建關係：user與host create table user2host( id int not null unique auto_increment, user_id int not null, host_id int not null, primary key(user_id,host_id), foreign key(user_id) references user(id), foreign key(host_id) references host(id) ); insert into user2host(user_id,host_id) values (1,1), (1,2), (1,3), (1,4), (1,5), (1,6), (1,7), (1,8), (1,9), (1,10), (1,11), (1,12), (1,13), (1,14), (1,15), (1,16), (2,2), (2,3), (2,4), (2,5), (3,10), (3,11), (3,12) ;
2.8 做業
第3章 MySQL之單表查詢
3.1 單表查詢的語法
SELECT 字段1,字段2... FROM 表名
WHERE 條件
GROUP BY field
HAVING 篩選
ORDER BY field
LIMIT 限制條數
單表語法： select distinct 字段1, 字段2,... from 表名 where 約束條件 group by 分組條件 having 過濾條件 order by 排序字段 limit n;
3.2 關鍵字的執行優先級(重點)
3.2.1 執行順序
重點中的重點：關鍵字的執行優先級
from
where
group by
having
select
distinct
order by
limit
3.2.2 執行順序解讀
1.找到表:from
2.拿着where指定的約束條件，去文件/表中取出一條條記錄
3.將取出的一條條記錄進行分組group by，若是沒有group by，則總體做爲一組
4.將分組的結果進行having過濾
5.執行select
6.去重
7.將結果按條件排序：order by
8.限制結果的顯示條數
3.3 簡單查詢
3.3.1 準備表和記錄
######################準備表和記錄###################### company.employee 員工id id int 姓名 emp_name varchar 性別 sex enum 年齡 age int 入職日期 hire_date date 崗位 post varchar 職位描述 post_comment varchar 薪水 salary double 辦公室 office int 部門編號 depart_id int #建立表 create table employee( id int not null unique auto_increment, name varchar(20) not null, sex enum('male','female') not null default 'male', #大部分是男的 age int(3) unsigned not null default 28, hire_date date not null, post varchar(50), post_comment varchar(100), salary double(15,2), office int, #一個部門一個屋子 depart_id int ); #查看錶結構 mysql> desc employee; +--------------+-----------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------+-----------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(20) | NO | | NULL | | | sex | enum('male','female') | NO | | male | | | age | int(3) unsigned | NO | | 28 | | | hire_date | date | NO | | NULL | | | post | varchar(50) | YES | | NULL | | | post_comment | varchar(100) | YES | | NULL | | | salary | double(15,2) | YES | | NULL | | | office | int(11) | YES | | NULL | | | depart_id | int(11) | YES | | NULL | | +--------------+-----------------------+------+-----+---------+----------------+ #插入記錄 #三個部門：教學，銷售，運營 insert into employee(name,sex,age,hire_date,post,salary,office,depart_id) values ('egon','male',18,'20170301','老男孩駐沙河辦事處外交大使',7300.33,401,1), #如下是教學部 ('alex','male',78,'20150302','teacher',1000000.31,401,1), ('wupeiqi','male',81,'20130305','teacher',8300,401,1), ('yuanhao','male',73,'20140701','teacher',3500,401,1), ('liwenzhou','male',28,'20121101','teacher',2100,401,1), ('jingliyang','female',18,'20110211','teacher',9000,401,1), ('jinxin','male',18,'19000301','teacher',30000,401,1), ('成龍','male',48,'20101111','teacher',10000,401,1), ('歪歪','female',48,'20150311','sale',3000.13,402,2),#如下是銷售部門 ('丫丫','female',38,'20101101','sale',2000.35,402,2), ('丁丁','female',18,'20110312','sale',1000.37,402,2), ('星星','female',18,'20160513','sale',3000.29,402,2), ('格格','female',28,'20170127','sale',4000.33,402,2), ('張野','male',28,'20160311','operation',10000.13,403,3), #如下是運營部門 ('程咬金','male',18,'19970312','operation',20000,403,3), ('程咬銀','female',18,'20130311','operation',19000,403,3), ('程咬銅','male',18,'20150411','operation',18000,403,3), ('程咬鐵','female',18,'20140512','operation',17000,403,3) ; #ps：若是在windows系統中，插入中文字符，select的結果爲空白，能夠將全部字符編碼統一設置成gbk
3.3.2 簡單查詢實例
#簡單查詢 SELECT id,name,sex,age,hire_date,post,post_comment,salary,office,depart_id FROM employee; SELECT * FROM employee; SELECT name,salary FROM employee; #避免重複DISTINCT SELECT DISTINCT post FROM employee; #經過四則運算查詢 SELECT name, salary*12 FROM employee; SELECT name, salary*12 AS Annual_salary FROM employee; SELECT name, salary*12 Annual_salary FROM employee; #定義顯示格式 CONCAT() 函數用於鏈接字符串 SELECT CONCAT('姓名: ',name,' 年薪: ', salary*12) AS Annual_salary FROM employee; CONCAT_WS() 第一個參數爲分隔符 SELECT CONCAT_WS(':',name,salary*12) AS Annual_salary FROM employee; 結合CASE語句： SELECT ( CASE WHEN NAME = 'egon' THEN NAME WHEN NAME = 'alex' THEN CONCAT(name,'_BIGSB') ELSE concat(NAME, 'SB') END ) as new_name FROM emp;
3.3.3 小練習
1 查出全部員工的名字，薪資,格式爲 <名字:egon> <薪資:3000> 2 查出全部的崗位（去掉重複） 3 查出全部員工名字，以及他們的年薪,年薪的字段名爲annual_year
select concat('<名字:',name,'> ','<薪資:',salary,'>') from employee; select distinct depart_id from employee; select name,salary*12 annual_salary from employee;
3.3.4 課堂實例
#一、簡單查詢 select * from emp; select id,name from emp; # 去除重複 select distinct post from emp; # 四則運算 select name,salary*12 as annual_salary from emp; select name,salary*12 annual_salary from emp; # 定義顯示格式 select concat('姓名: ',name) as new_name, concat('年薪: ',salary*12) as annual_salary from emp; select concat(name,'_SB') as new_name from emp; select concat(name,'_SB') as new_name from emp where name != 'egon'; select ( case when name = 'egon' then name when name = 'alex' then concat(name,'_BIGSB') else concat(name,'_SB') end ) as new_name from emp; select concat(name,':',salary,':',sex) from emp; select concat_ws(':',name,salary,sex) from emp;
3.4 WHERE約束
3.4.1 介紹
where字句中可使用：
1. 比較運算符：> < >= <= <> !=
2. between 80 and 100 值在10到20之間
3. in(80,90,100) 值是10或20或30
4. like 'egon%'
pattern能夠是%或_，
%表示任意多字符
_表示一個字符
5. 邏輯運算符：在多個條件直接可使用邏輯運算符 and or not
3.4.2 實例
#1:單條件查詢 SELECT name FROM employee WHERE post='sale'; #2:多條件查詢 SELECT name,salary FROM employee WHERE post='teacher' AND salary>10000; #3:關鍵字BETWEEN AND SELECT name,salary FROM employee WHERE salary BETWEEN 10000 AND 20000; SELECT name,salary FROM employee WHERE salary NOT BETWEEN 10000 AND 20000; #4:關鍵字IS NULL(判斷某個字段是否爲NULL不能用等號，須要用IS) SELECT name,post_comment FROM employee WHERE post_comment IS NULL; SELECT name,post_comment FROM employee WHERE post_comment IS NOT NULL; SELECT name,post_comment FROM employee WHERE post_comment=''; 注意''是空字符串，不是null ps： 執行 update employee set post_comment='' where id=2; 再用上條查看，就會有結果了 #5:關鍵字IN集合查詢 SELECT name,salary FROM employee WHERE salary=3000 OR salary=3500 OR salary=4000 OR salary=9000 ; SELECT name,salary FROM employee WHERE salary IN (3000,3500,4000,9000) ; SELECT name,salary FROM employee WHERE salary NOT IN (3000,3500,4000,9000) ; #6:關鍵字LIKE模糊查詢 通配符’%’ SELECT * FROM employee WHERE name LIKE 'eg%'; 通配符’_’ SELECT * FROM employee WHERE name LIKE 'al__';
3.4.3 小練習
1. 查看崗位是teacher的員工姓名、年齡
2. 查看崗位是teacher且年齡大於30歲的員工姓名、年齡
3. 查看崗位是teacher且薪資在9000-1000範圍內的員工姓名、年齡、薪資
4. 查看崗位描述不爲NULL的員工信息
5. 查看崗位是teacher且薪資是10000或9000或30000的員工姓名、年齡、薪資
6. 查看崗位是teacher且薪資不是10000或9000或30000的員工姓名、年齡、薪資
7. 查看崗位是teacher且名字是jin開頭的員工姓名、年薪
select name,age from employee where post = 'teacher'; select name,age from employee where post='teacher' and age > 30; select name,age,salary from employee where post='teacher' and salary between 9000 and 10000; select * from employee where post_comment is not null; select name,age,salary from employee where post='teacher' and salary in (10000,9000,30000); select name,age,salary from employee where post='teacher' and salary not in (10000,9000,30000); select name,salary*12 from employee where post='teacher' and name like 'jin%';
3.4.4 課堂實例
2、where約束 select id,name,age from emp where age > 20; select id,name,age from emp where age >= 20 and age <= 38; select id,name,age from emp where age between 20 and 38; select id,name,age from emp where age <= 20 or age >= 38; select id,name,age from emp where age not between 20 and 38; select * from emp where age=18 or age=28 or age=38; select * from emp where age in (18,28,38); select * from emp where age=18 or sex='male'; select * from emp where name like 'jin%'; select * from emp where name like '__';
3.5 分組查詢:GROUP BY
3.5.1 什麼是分組？爲何要分組？
#一、首先明確一點：分組發生在where以後，即分組是基於where以後獲得的記錄而進行的
#二、分組指的是：將全部記錄按照某個相同字段進行歸類，好比針對員工信息表的職位分組，或者按照性別進行分組等
#三、爲什麼要分組呢？
取每一個部門的最高工資
取每一個部門的員工數
取男人數和女人數
小竅門：‘每’這個字後面的字段，就是咱們分組的依據
#四、大前提：
能夠按照任意字段分組，可是分組完畢後，好比group by post，只能查看post字段，若是想查看組內信息，須要藉助於聚合函數
3.5.2 ONLY_FULL_GROUP_BY
###############！！！SQL_MODE設置！！！####################### #查看MySQL 5.7默認的sql_mode以下： mysql> select @@global.sql_mode; ONLY_FULL_GROUP_BY,STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION #！！！注意 ONLY_FULL_GROUP_BY的語義就是肯定select target list中的全部列的值都是明確語義，簡單的說來，在ONLY_FULL_GROUP_BY模式下，target list中的值要麼是來自於彙集函數的結果，要麼是來自於group by list中的表達式的值。 #設置sql_mole以下操做(咱們能夠去掉ONLY_FULL_GROUP_BY模式)： mysql> set global sql_mode='STRICT_TRANS_TABLES,NO_ZERO_IN_DATE,NO_ZERO_DATE,ERROR_FOR_DIVISION_BY_ZERO,NO_AUTO_CREATE_USER,NO_ENGINE_SUBSTITUTION';
3.5.3 實例
mysql> select @@global.sql_mode; +-------------------+ | @@global.sql_mode | +-------------------+ | | +-------------------+ row in set (0.00 sec) mysql> select * from emp group by post; +----+------+--------+-----+------------+----------------------------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------+--------+-----+------------+----------------------------+--------------+------------+--------+-----------+ | 14 | 張野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | | 1 | egon | male | 18 | 2017-03-01 | 老男孩駐沙河辦事處外交大使 | NULL | 7300.33 | 401 | 1 | +----+------+--------+-----+------------+----------------------------+--------------+------------+--------+-----------+ rows in set (0.00 sec) #因爲沒有設置ONLY_FULL_GROUP_BY,因而也能夠有結果，默認都是組內的第一條記錄，但其實這是沒有意義的 mysql> set global sql_mode='ONLY_FULL_GROUP_BY'; Query OK, 0 rows affected (0.00 sec) mysql> quit #設置成功後，必定要退出，而後從新登陸方可生效 Bye mysql> use db1; Database changed mysql> select * from emp group by post; #報錯 ERROR 1055 (42000): 'db1.emp.id' isn't in GROUP BY mysql> select post,count(id) from emp group by post; #只能查看分組依據和使用聚合函數 +----------------------------+-----------+ | post | count(id) | +----------------------------+-----------+ | operation | 5 | | sale | 5 | | teacher | 7 | | 老男孩駐沙河辦事處外交大使 | 1 | +----------------------------+-----------+ rows in set (0.00 sec)
3.5.4 GROUP BY
單獨使用GROUP BY關鍵字分組 SELECT post FROM employee GROUP BY post; 注意：咱們按照post字段分組，那麼select查詢的字段只能是post，想要獲取組內的其餘相關信息，須要藉助函數 GROUP BY關鍵字和GROUP_CONCAT()函數一塊兒使用 SELECT post,GROUP_CONCAT(name) FROM employee GROUP BY post;#按照崗位分組，並查看組內成員名 SELECT post,GROUP_CONCAT(name) as emp_members FROM employee GROUP BY post; GROUP BY與聚合函數一塊兒使用 select post,count(id) as count from employee group by post;#按照崗位分組，並查看每一個組有多少人
強調：
若是咱們用unique的字段做爲分組的依據，則每一條記錄自成一組，這種分組沒有意義
多條記錄之間的某個字段值相同，該字段一般用來做爲分組的依據
3.5.5 聚合函數
#強調：聚合函數聚合的是組的內容，如果沒有分組，則默認一組 示例： SELECT COUNT(*) FROM employee; SELECT COUNT(*) FROM employee WHERE depart_id=1; SELECT MAX(salary) FROM employee; SELECT MIN(salary) FROM employee; SELECT AVG(salary) FROM employee; SELECT SUM(salary) FROM employee; SELECT SUM(salary) FROM employee WHERE depart_id=3;
3.5.6 小練習
1. 查詢崗位名以及崗位包含的全部員工名字
2. 查詢崗位名以及各崗位內包含的員工個數
3. 查詢公司內男員工和女員工的個數
4. 查詢崗位名以及各崗位的平均薪資
5. 查詢崗位名以及各崗位的最高薪資
6. 查詢崗位名以及各崗位的最低薪資
7. 查詢男員工與男員工的平均薪資，女員工與女員工的平均薪資
#題1：分組 mysql> select post,group_concat(name) from employee group by post; +-----------------------------------------+---------------------------------------------------------+ | post | group_concat(name) | +-----------------------------------------+---------------------------------------------------------+ | operation | 張野,程咬金,程咬銀,程咬銅,程咬鐵 | | sale | 歪歪,丫丫,丁丁,星星,格格 | | teacher | alex,wupeiqi,yuanhao,liwenzhou,jingliyang,jinxin,成龍 | | 老男孩駐沙河辦事處外交大使 | egon | +-----------------------------------------+---------------------------------------------------------+ #題目2： mysql> select post,count(id) from employee group by post; +-----------------------------------------+-----------+ | post | count(id) | +-----------------------------------------+-----------+ | operation | 5 | | sale | 5 | | teacher | 7 | | 老男孩駐沙河辦事處外交大使 | 1 | +-----------------------------------------+-----------+ #題目3： mysql> select sex,count(id) from employee group by sex; +--------+-----------+ | sex | count(id) | +--------+-----------+ | male | 10 | | female | 8 | +--------+-----------+ #題目4： mysql> select post,avg(salary) from employee group by post; +-----------------------------------------+---------------+ | post | avg(salary) | +-----------------------------------------+---------------+ | operation | 16800.026000 | | sale | 2600.294000 | | teacher | 151842.901429 | | 老男孩駐沙河辦事處外交大使 | 7300.330000 | +-----------------------------------------+---------------+ #題目5 mysql> select post,max(salary) from employee group by post; +-----------------------------------------+-------------+ | post | max(salary) | +-----------------------------------------+-------------+ | operation | 20000.00 | | sale | 4000.33 | | teacher | 1000000.31 | | 老男孩駐沙河辦事處外交大使 | 7300.33 | +-----------------------------------------+-------------+ #題目6 mysql> select post,min(salary) from employee group by post; +-----------------------------------------+-------------+ | post | min(salary) | +-----------------------------------------+-------------+ | operation | 10000.13 | | sale | 1000.37 | | teacher | 2100.00 | | 老男孩駐沙河辦事處外交大使 | 7300.33 | +-----------------------------------------+-------------+ #題目七 mysql> select sex,avg(salary) from employee group by sex; +--------+---------------+ | sex | avg(salary) | +--------+---------------+ | male | 110920.077000 | | female | 7250.183750 | +--------+---------------+
3.5.7 課堂實例
3、group by分組 分組依據應該找重複度比較高的字段 分組以後只能查到分組字段，或者聚合的結果 set global sql_mode='strict_trans_tables,only_full_group_by'; select post,max(salary) from emp group by post; select post,min(salary) from emp group by post; select post,sum(salary) from emp group by post; select post,avg(salary) from emp group by post; select post,count(id) from emp group by post; select post,group_concat(name) from emp group by post; select count(id) from emp; select count(id) from emp where max(salary) > 1;
3.6 HAVING過濾
3.6.1 介紹
HAVING與WHERE不同的地方在於!!!!!!
#！！！執行優先級從高到低：where > group by > having
#1. Where 發生在分組group by以前，於是Where中能夠有任意字段，可是絕對不能使用聚合函數。
#2. Having發生在分組group by以後，於是Having中可使用分組的字段，沒法直接取到其餘字段,可使用聚合函數
###################################驗證######################################## mysql> select @@sql_mode; +--------------------+ | @@sql_mode | +--------------------+ | ONLY_FULL_GROUP_BY | +--------------------+ row in set (0.00 sec) mysql> select * from emp where salary > 100000; +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ | 2 | alex | male | 78 | 2015-03-02 | teacher | NULL | 1000000.31 | 401 | 1 | +----+------+------+-----+------------+---------+--------------+------------+--------+-----------+ row in set (0.00 sec) mysql> select * from emp having salary > 100000; ERROR 1463 (42000): Non-grouping field 'salary' is used in HAVING clause mysql> select post,group_concat(name) from emp group by post having salary > 10000;#錯誤，分組後沒法直接取到salary字段 ERROR 1054 (42S22): Unknown column 'salary' in 'having clause' mysql> select post,group_concat(name) from emp group by post having avg(salary) > 10000; +-----------+-------------------------------------------------------+ | post | group_concat(name) | +-----------+-------------------------------------------------------+ | operation | 程咬鐵,程咬銅,程咬銀,程咬金,張野 | | teacher | 成龍,jinxin,jingliyang,liwenzhou,yuanhao,wupeiqi,alex | +-----------+-------------------------------------------------------+ rows in set (0.00 sec)
3.6.2 小練習
1. 查詢各崗位內包含的員工個數小於2的崗位名、崗位內包含員工名字、個數
3. 查詢各崗位平均薪資大於10000的崗位名、平均工資
4. 查詢各崗位平均薪資大於10000且小於20000的崗位名、平均工資
#題1： mysql> select post,group_concat(name),count(id) from employee group by post having count(id) < 2; +-----------------------------------------+--------------------+-----------+ | post | group_concat(name) | count(id) | +-----------------------------------------+--------------------+-----------+ | 老男孩駐沙河辦事處外交大使 | egon | 1 | +-----------------------------------------+--------------------+-----------+ #題目2： mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000; +-----------+---------------+ | post | avg(salary) | +-----------+---------------+ | operation | 16800.026000 | | teacher | 151842.901429 | +-----------+---------------+ #題目3： mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 and avg(salary) <20000; +-----------+--------------+ | post | avg(salary) | +-----------+--------------+ | operation | 16800.026000 | +-----------+--------------+
3.6.3 課堂實例
4: having 過濾條件 select post,avg(salary) from emp group by post having avg(salary) > 20000;
3.7 查詢排序:ORDER BY
按單列排序
SELECT * FROM employee ORDER BY salary;
SELECT * FROM employee ORDER BY salary ASC;
SELECT * FROM employee ORDER BY salary DESC;
按多列排序:先按照age排序，若是年紀相同，則按照薪資排序
SELECT * from employee
ORDER BY age,
salary DESC;
3.7.1 小練習
1. 查詢全部員工信息，先按照age升序排序，若是age相同則按照hire_date降序排序
2. 查詢各崗位平均薪資大於10000的崗位名、平均工資,結果按平均薪資升序排列
3. 查詢各崗位平均薪資大於10000的崗位名、平均工資,結果按平均薪資降序排列
#題目1 mysql> select * from employee ORDER BY age asc,hire_date desc; #題目2 mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 order by avg(salary) asc; +-----------+---------------+ | post | avg(salary) | +-----------+---------------+ | operation | 16800.026000 | | teacher | 151842.901429 | +-----------+---------------+ #題目3 mysql> select post,avg(salary) from employee group by post having avg(salary) > 10000 order by avg(salary) desc; +-----------+---------------+ | post | avg(salary) | +-----------+---------------+ | teacher | 151842.901429 | | operation | 16800.026000 | +-----------+---------------+
3.7.2 課堂實例
5: order by排序 select * from emp order by age asc; # 默認升序，從小到大 select * from emp order by age desc; #從大到小 select * from emp order by age asc,id desc; select post,avg(salary) from emp group by post order by avg(salary);
3.8 限制查詢的記錄數:LIMIT
3.8.1 示例
示例： SELECT * FROM employee ORDER BY salary DESC LIMIT 3; #默認初始位置爲0 SELECT * FROM employee ORDER BY salary DESC LIMIT 0,5; #從第0開始，即先查詢出第一條，而後包含這一條在內日後查5條 SELECT * FROM employee ORDER BY salary DESC LIMIT 5,5; #從第5開始，即先查詢出第6條，而後包含這一條在內日後查5條
3.8.2 小練習
1. 分頁顯示，每頁5條
mysql> select * from employee limit 0,5; +----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ | 1 | egon | male | 18 | 2017-03-01 | 老男孩駐沙河辦事處外交大使 | NULL | 7300.33 | 401 | 1 | | 2 | alex | male | 78 | 2015-03-02 | teacher | | 1000000.31 | 401 | 1 | | 3 | wupeiqi | male | 81 | 2013-03-05 | teacher | NULL | 8300.00 | 401 | 1 | | 4 | yuanhao | male | 73 | 2014-07-01 | teacher | NULL | 3500.00 | 401 | 1 | | 5 | liwenzhou | male | 28 | 2012-11-01 | teacher | NULL | 2100.00 | 401 | 1 | +----+-----------+------+-----+------------+-----------------------------------------+--------------+------------+--------+-----------+ rows in set (0.00 sec) mysql> select * from employee limit 5,5; +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ | 6 | jingliyang | female | 18 | 2011-02-11 | teacher | NULL | 9000.00 | 401 | 1 | | 7 | jinxin | male | 18 | 1900-03-01 | teacher | NULL | 30000.00 | 401 | 1 | | 8 | 成龍 | male | 48 | 2010-11-11 | teacher | NULL | 10000.00 | 401 | 1 | | 9 | 歪歪 | female | 48 | 2015-03-11 | sale | NULL | 3000.13 | 402 | 2 | | 10 | 丫丫 | female | 38 | 2010-11-01 | sale | NULL | 2000.35 | 402 | 2 | +----+------------+--------+-----+------------+---------+--------------+----------+--------+-----------+ rows in set (0.00 sec) mysql> select * from employee limit 10,5; +----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ | id | name | sex | age | hire_date | post | post_comment | salary | office | depart_id | +----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ | 11 | 丁丁 | female | 18 | 2011-03-12 | sale | NULL | 1000.37 | 402 | 2 | | 12 | 星星 | female | 18 | 2016-05-13 | sale | NULL | 3000.29 | 402 | 2 | | 13 | 格格 | female | 28 | 2017-01-27 | sale | NULL | 4000.33 | 402 | 2 | | 14 | 張野 | male | 28 | 2016-03-11 | operation | NULL | 10000.13 | 403 | 3 | | 15 | 程咬金 | male | 18 | 1997-03-12 | operation | NULL | 20000.00 | 403 | 3 | +----+-----------+--------+-----+------------+-----------+--------------+----------+--------+-----------+ rows in set (0.00 sec)
3.8.3 課堂實例
6、limit n select * from emp limit 3; select * from emp limit 0,5; select * from emp limit 5,5; select * from emp limit 10,5; select * from emp limit 15,5; def from(db,table): f=open(filepath,'r') return f def where(f,pattern): for line in f: if pattern: yield line def group(): pass def having(): pass def distinct(): pass def order(): pass def limit(): pass def select(): f=from(db,table) lines=where(f,'id > 1') group_res=group(lines) having_res=having(group_res) distinct_res=distinct(having_res) order_res=order(distinct_res) res=limit(order_res) print(res)
3.9 使用正則表達式查詢
SELECT * FROM employee WHERE name REGEXP '^ale'; SELECT * FROM employee WHERE name REGEXP 'on$'; SELECT * FROM employee WHERE name REGEXP 'm{2}'; 小結：對字符串匹配的方式 WHERE name = 'egon'; WHERE name LIKE 'yua%'; WHERE name REGEXP 'on$';
3.9.1 小練習
查看全部員工中名字是jin開頭，n或者g結果的員工信息
select * from employee where name regexp '^jin.*[gn]$';
3.9.2 課堂實例
# 正則
select * from emp where name regexp '^jin.*$';
第4章 MySQL之多表查詢
4.1 介紹
本節主題
l 多表鏈接查詢
l 複合條件鏈接查詢
l 子查詢
4.1.1 準備表
#################表department與employee################## #建表 create table department( id int, name varchar(20) ); create table employee( id int primary key auto_increment, name varchar(20), sex enum('male','female') not null default 'male', age int, dep_id int ); #插入數據 insert into department values (200,'技術'), (201,'人力資源'), (202,'銷售'), (203,'運營'); insert into employee(name,sex,age,dep_id) values ('egon','male',18,200), ('alex','female',48,201), ('wupeiqi','male',38,201), ('yuanhao','female',28,202), ('liwenzhou','male',18,200), ('jingliyang','female',18,204) ; #查看錶結構和數據 mysql> desc department; +-------+-------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+-------------+------+-----+---------+-------+ | id | int(11) | YES | | NULL | | | name | varchar(20) | YES | | NULL | | +-------+-------------+------+-----+---------+-------+ mysql> desc employee; +--------+-----------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------+-----------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(20) | YES | | NULL | | | sex | enum('male','female') | NO | | male | | | age | int(11) | YES | | NULL | | | dep_id | int(11) | YES | | NULL | | +--------+-----------------------+------+-----+---------+----------------+ mysql> select * from department; +------+--------------+ | id | name | +------+--------------+ | 200 | 技術 | | 201 | 人力資源 | | 202 | 銷售 | | 203 | 運營 | +------+--------------+ mysql> select * from employee; +----+------------+--------+------+--------+ | id | name | sex | age | dep_id | +----+------------+--------+------+--------+ | 1 | egon | male | 18 | 200 | | 2 | alex | female | 48 | 201 | | 3 | wupeiqi | male | 38 | 201 | | 4 | yuanhao | female | 28 | 202 | | 5 | liwenzhou | male | 18 | 200 | | 6 | jingliyang | female | 18 | 204 | +----+------------+--------+------+--------+
4.2 多表鏈接查詢
#重點：外連接語法
SELECT 字段列表
FROM 表1 INNER|LEFT|RIGHT JOIN 表2
ON 表1.字段 = 表2.字段;
4.2.1 交叉鏈接：不適用任何匹配條件。生成笛卡爾積
mysql> select * from employee,department; +----+------------+--------+------+--------+------+--------------+ | id | name | sex | age | dep_id | id | name | +----+------------+--------+------+--------+------+--------------+ | 1 | egon | male | 18 | 200 | 200 | 技術 | | 1 | egon | male | 18 | 200 | 201 | 人力資源 | | 1 | egon | male | 18 | 200 | 202 | 銷售 | | 1 | egon | male | 18 | 200 | 203 | 運營 | | 2 | alex | female | 48 | 201 | 200 | 技術 | | 2 | alex | female | 48 | 201 | 201 | 人力資源 | | 2 | alex | female | 48 | 201 | 202 | 銷售 | | 2 | alex | female | 48 | 201 | 203 | 運營 | | 3 | wupeiqi | male | 38 | 201 | 200 | 技術 | | 3 | wupeiqi | male | 38 | 201 | 201 | 人力資源 | | 3 | wupeiqi | male | 38 | 201 | 202 | 銷售 | | 3 | wupeiqi | male | 38 | 201 | 203 | 運營 | | 4 | yuanhao | female | 28 | 202 | 200 | 技術 | | 4 | yuanhao | female | 28 | 202 | 201 | 人力資源 | | 4 | yuanhao | female | 28 | 202 | 202 | 銷售 | | 4 | yuanhao | female | 28 | 202 | 203 | 運營 | | 5 | liwenzhou | male | 18 | 200 | 200 | 技術 | | 5 | liwenzhou | male | 18 | 200 | 201 | 人力資源 | | 5 | liwenzhou | male | 18 | 200 | 202 | 銷售 | | 5 | liwenzhou | male | 18 | 200 | 203 | 運營 | | 6 | jingliyang | female | 18 | 204 | 200 | 技術 | | 6 | jingliyang | female | 18 | 204 | 201 | 人力資源 | | 6 | jingliyang | female | 18 | 204 | 202 | 銷售 | | 6 | jingliyang | female | 18 | 204 | 203 | 運營 | +----+------------+--------+------+--------+------+--------------+
4.2.2 內鏈接：只鏈接匹配的行
#找兩張表共有的部分，至關於利用條件從笛卡爾積結果中篩選出了正確的結果 #department沒有204這個部門，於是employee表中關於204這條員工信息沒有匹配出來 mysql> select employee.id,employee.name,employee.age,employee.sex,department.name from employee inner join department on employee.dep_id=department.id; +----+-----------+------+--------+--------------+ | id | name | age | sex | name | +----+-----------+------+--------+--------------+ | 1 | egon | 18 | male | 技術 | | 2 | alex | 48 | female | 人力資源 | | 3 | wupeiqi | 38 | male | 人力資源 | | 4 | yuanhao | 28 | female | 銷售 | | 5 | liwenzhou | 18 | male | 技術 | +----+-----------+------+--------+--------------+ #上述sql等同於 mysql> select employee.id,employee.name,employee.age,employee.sex,department.name from employee,department where employee.dep_id=department.id;
4.2.3 外連接之左鏈接：優先顯示左表所有記錄
#以左表爲準，即找出全部員工信息，固然包括沒有部門的員工 #本質就是：在內鏈接的基礎上增長左邊有右邊沒有的結果 mysql> select employee.id,employee.name,department.name as depart_name from employee left join department on employee.dep_id=department.id; +----+------------+--------------+ | id | name | depart_name | +----+------------+--------------+ | 1 | egon | 技術 | | 5 | liwenzhou | 技術 | | 2 | alex | 人力資源 | | 3 | wupeiqi | 人力資源 | | 4 | yuanhao | 銷售 | | 6 | jingliyang | NULL | +----+------------+--------------+
4.2.4 外連接之右鏈接：優先顯示右表所有記錄
#以右表爲準，即找出全部部門信息，包括沒有員工的部門 #本質就是：在內鏈接的基礎上增長右邊有左邊沒有的結果 mysql> select employee.id,employee.name,department.name as depart_name from employee right join department on employee.dep_id=department.id; +------+-----------+--------------+ | id | name | depart_name | +------+-----------+--------------+ | 1 | egon | 技術 | | 2 | alex | 人力資源 | | 3 | wupeiqi | 人力資源 | | 4 | yuanhao | 銷售 | | 5 | liwenzhou | 技術 | | NULL | NULL | 運營 | +------+-----------+--------------+
4.2.5 全外鏈接：顯示左右兩個表所有記錄
全外鏈接：在內鏈接的基礎上增長左邊有右邊沒有的和右邊有左邊沒有的結果 #注意：mysql不支持全外鏈接 full JOIN #強調：mysql可使用此種方式間接實現全外鏈接 select * from employee left join department on employee.dep_id = department.id union select * from employee right join department on employee.dep_id = department.id ; #查看結果 +------+------------+--------+------+--------+------+--------------+ | id | name | sex | age | dep_id | id | name | +------+------------+--------+------+--------+------+--------------+ | 1 | egon | male | 18 | 200 | 200 | 技術 | | 5 | liwenzhou | male | 18 | 200 | 200 | 技術 | | 2 | alex | female | 48 | 201 | 201 | 人力資源 | | 3 | wupeiqi | male | 38 | 201 | 201 | 人力資源 | | 4 | yuanhao | female | 28 | 202 | 202 | 銷售 | | 6 | jingliyang | female | 18 | 204 | NULL | NULL | | NULL | NULL | NULL | NULL | NULL | 203 | 運營 | +------+------------+--------+------+--------+------+--------------+ #注意 union與union all的區別：union會去掉相同的紀錄
4.2.6 符合條件鏈接查詢
#示例1：之內鏈接的方式查詢employee和department表，而且employee表中的age字段值必須大於25,即找出年齡大於25歲的員工以及員工所在的部門 select employee.name,department.name from employee inner join department on employee.dep_id = department.id where age > 25; #示例2：之內鏈接的方式查詢employee和department表，而且以age字段的升序方式顯示 select employee.id,employee.name,employee.age,department.name from employee,department where employee.dep_id = department.id and age > 25 order by age asc;
4.2.7 課堂實例
#一、笛卡爾積 select * from emp,dep; select * from emp,dep where emp.dep_id=dep.id; #二、內鏈接inner join：取兩張表的共同部分 select * from emp inner join dep on emp.dep_id=dep.id; #三、左鏈接left join：在內鏈接的基礎上保留左表的記錄 select * from emp left join dep on emp.dep_id=dep.id; #四、右鏈接right join：在內鏈接的基礎上保留右表的記錄 select * from emp right join dep on emp.dep_id=dep.id; #五、全外鏈接full join：在內鏈接的基礎上保留左、右表的記錄 select * from emp left join dep on emp.dep_id=dep.id union select * from emp right join dep on emp.dep_id=dep.id;
4.3 子查詢
#1：子查詢是將一個查詢語句嵌套在另外一個查詢語句中。
#2：內層查詢語句的查詢結果，能夠爲外層查詢語句提供查詢條件。
#3：子查詢中能夠包含：IN、NOT IN、ANY、ALL、EXISTS 和 NOT EXISTS等關鍵字
#4：還能夠包含比較運算符：= 、 !=、> 、<等
4.3.1 帶IN關鍵字的子查詢
#查詢平均年齡在25歲以上的部門名 select id,name from department where id in (select dep_id from employee group by dep_id having avg(age) > 25); #查看技術部員工姓名 select name from employee where dep_id in (select id from department where name='技術'); #查看不足1人的部門名(子查詢獲得的是有人的部門id)select name from department where id not in (select distinct dep_id from employee);
4.3.2 帶比較運算符的子查詢
#比較運算符：=、!=、>、>=、<、<=、<> #查詢大於全部人平均年齡的員工名與年齡 mysql> select name,age from emp where age > (select avg(age) from emp); +---------+------+ | name | age | +---------+------+ | alex | 48 | | wupeiqi | 38 | +---------+------+ rows in set (0.00 sec) #查詢大於部門內平均年齡的員工名、年齡 select t1.name,t1.age from emp t1 inner join (select dep_id,avg(age) avg_age from emp group by dep_id) t2 on t1.dep_id = t2.dep_id where t1.age > t2.avg_age;
4.3.3 帶EXISTS關鍵字的子查詢
EXISTS關字鍵字表示存在。在使用EXISTS關鍵字時，內層查詢語句不返回查詢的記錄。
而是返回一個真假值。True或False
當返回True時，外層查詢語句將進行查詢；當返回值爲False時，外層查詢語句不進行查詢
#department表中存在dept_id=203，Ture mysql> select * from employee -> where exists -> (select id from department where id=200); +----+------------+--------+------+--------+ | id | name | sex | age | dep_id | +----+------------+--------+------+--------+ | 1 | egon | male | 18 | 200 | | 2 | alex | female | 48 | 201 | | 3 | wupeiqi | male | 38 | 201 | | 4 | yuanhao | female | 28 | 202 | | 5 | liwenzhou | male | 18 | 200 | | 6 | jingliyang | female | 18 | 204 | +----+------------+--------+------+--------+ #department表中存在dept_id=205，False mysql> select * from employee -> where exists -> (select id from department where id=204); Empty set (0.00 sec)
4.3.4 課堂實例
1 帶IN關鍵字的子查詢 #查詢平均年齡在25歲以上的部門名 select name from dep where id in (select dep_id from emp group by dep_id having avg(age) > 25); #查看技術部員工姓名 select emp.name from emp inner join dep on emp.dep_id = dep.id where dep.name = '技術' ; select name from emp where dep_id =(select id from dep where name='技術'); #查看不足1人的部門名 select name from dep where id not in ( select dep_id from emp group by dep_id having count(id) >= 1); select name from dep where id not in ( select distinct dep_id from emp); #查詢大於全部人平均年齡的員工名與年齡 select name,age from emp where age > ( select avg(age) from emp); #查詢大於部門內平均年齡的員工名、年齡 select t1.* from emp as t1 inner join (select dep_id,avg(age) as avg_age from emp group by dep_id) as t2 on t1.dep_id = t2.dep_id where t1.age > t2.avg_age ; # 統計每一個部門最新入職的員工名，入職日期 select t1.name,t1.hire_date from emp as t1 inner join (select post,max(hire_date) max_date from emp group by post) as t2 on t1.post = t2.post where t1.hire_date = t2.max_date ; select name from emp where name='egon'; select name from emp where id > 1000; select name from emp where id > 1000 and id < 1005; select name from emp where id = 1000; select name from emp where salary = 20000/12; select * from emp;
4.3.5 練習：查詢每一個部門最新入職的那位員工
#########################準備表和記錄############################# company.employee 員工id id int 姓名 emp_name varchar 性別 sex enum 年齡 age int 入職日期 hire_date date 崗位 post varchar 職位描述 post_comment varchar 薪水 salary double 辦公室 office int 部門編號 depart_id int #建立表 create table employee( id int not null unique auto_increment, name varchar(20) not null, sex enum('male','female') not null default 'male', #大部分是男的 age int(3) unsigned not null default 28, hire_date date not null, post varchar(50), post_comment varchar(100), salary double(15,2), office int, #一個部門一個屋子 depart_id int ); #查看錶結構 mysql> desc employee; +--------------+-----------------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +--------------+-----------------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | name | varchar(20) | NO | | NULL | | | sex | enum('male','female') | NO | | male | | | age | int(3) unsigned | NO | | 28 | | | hire_date | date | NO | | NULL | | | post | varchar(50) | YES | | NULL | | | post_comment | varchar(100) | YES | | NULL | | | salary | double(15,2) | YES | | NULL | | | office | int(11) | YES | | NULL | | | depart_id | int(11) | YES | | NULL | | +--------------+-----------------------+------+-----+---------+----------------+ #插入記錄 #三個部門：教學，銷售，運營 insert into employee(name,sex,age,hire_date,post,salary,office,depart_id) values ('egon','male',18,'20170301','老男孩駐沙河辦事處外交大使',7300.33,401,1), #如下是教學部 ('alex','male',78,'20150302','teacher',1000000.31,401,1), ('wupeiqi','male',81,'20130305','teacher',8300,401,1), ('yuanhao','male',73,'20140701','teacher',3500,401,1), ('liwenzhou','male',28,'20121101','teacher',2100,401,1), ('jingliyang','female',18,'20110211','teacher',9000,401,1), ('jinxin','male',18,'19000301','teacher',30000,401,1), ('成龍','male',48,'20101111','teacher',10000,401,1), ('歪歪','female',48,'20150311','sale',3000.13,402,2),#如下是銷售部門 ('丫丫','female',38,'20101101','sale',2000.35,402,2), ('丁丁','female',18,'20110312','sale',1000.37,402,2), ('星星','female',18,'20160513','sale',3000.29,402,2), ('格格','female',28,'20170127','sale',4000.33,402,2), ('張野','male',28,'20160311','operation',10000.13,403,3), #如下是運營部門 ('程咬金','male',18,'19970312','operation',20000,403,3), ('程咬銀','female',18,'20130311','operation',19000,403,3), ('程咬銅','male',18,'20150411','operation',18000,403,3), ('程咬鐵','female',18,'20140512','operation',17000,403,3) ; #ps：若是在windows系統中，插入中文字符，select的結果爲空白，能夠將全部字符編碼統一設置成gbk
################################答案一（鏈表）############################### SELECT * FROM emp AS t1 INNER JOIN ( SELECT post, max(hire_date) max_date FROM emp GROUP BY post ) AS t2 ON t1.post = t2.post WHERE t1.hire_date = t2.max_date;
#####################答案二（子查詢）########################### mysql> select (select t2.name from emp as t2 where t2.post=t1.post order by hire_date desc limit 1) from emp as t1 group by post; +---------------------------------------------------------------------------------------+ | (select t2.name from emp as t2 where t2.post=t1.post order by hire_date desc limit 1) | +---------------------------------------------------------------------------------------+ | 張野 | | 格格 | | alex | | egon | +---------------------------------------------------------------------------------------+ rows in set (0.00 sec) mysql> select (select t2.id from emp as t2 where t2.post=t1.post order by hire_date desc limit 1) from emp as t1 group by post; +-------------------------------------------------------------------------------------+ | (select t2.id from emp as t2 where t2.post=t1.post order by hire_date desc limit 1) | +-------------------------------------------------------------------------------------+ | 14 | | 13 | | 2 | | 1 | +-------------------------------------------------------------------------------------+ rows in set (0.00 sec) #正確答案 mysql> select t3.name,t3.post,t3.hire_date from emp as t3 where id in (select (select id from emp as t2 where t2.post=t1.post order by hire_date desc limit 1) from emp as t1 group by post); +--------+-----------------------------------------+------------+ | name | post | hire_date | +--------+-----------------------------------------+------------+ | egon | 老男孩駐沙河辦事處外交大使 | 2017-03-01 | | alex | teacher | 2015-03-02 | | 格格 | sale | 2017-01-27 | | 張野 | operation | 2016-03-11 | +--------+-----------------------------------------+------------+ rows in set (0.00 sec)
答案一爲正確答案，答案二中的limit 1有問題（每一個部門可能有>1個爲同一時間入職的新員工），我只是想用該例子來講明能夠在select後使用子查詢
能夠基於上述方法解決：好比某網站在全國各個市都有站點，每一個站點一條數據，想取每一個省下最新的那一條市的網站質量信息
4.4 慢查詢優化的基本步驟
0.先運行看看是否真的很慢，注意設置SQL_NO_CACHE 1.where條件單表查，鎖定最小返回記錄表。這句話的意思是把查詢語句的where都應用到表中返回的記錄數最小的表開始查起，單表每一個字段分別查詢，看哪一個字段的區分度最高 2.explain查看執行計劃，是否與1預期一致（從鎖定記錄較少的表開始查詢） 3.order by limit 形式的sql語句讓排序的表優先查 4.瞭解業務方使用場景 5.加索引時參照建索引的幾大原則 6.觀察結果，不符合預期繼續從0分析
4.5 慢日誌管理
慢日誌 - 執行時間 > 10 - 未命中索引 - 日誌文件路徑 配置： - 內存 show variables like '%query%'; show variables like '%queries%'; set global 變量名 = 值 - 配置文件 mysqld --defaults-file='E:\wupeiqi\mysql-5.7.16-winx64\mysql-5.7.16-winx64\my-default.ini' my.conf內容： slow_query_log = ON slow_query_log_file = D:/.... 注意：修改配置文件以後，須要重啓服務
################################日誌管理############################### MySQL日誌管理 ======================================================== 錯誤日誌: 記錄 MySQL 服務器啓動、關閉及運行錯誤等信息 二進制日誌: 又稱binlog日誌，以二進制文件的方式記錄數據庫中除 SELECT 之外的操做 查詢日誌: 記錄查詢的信息 慢查詢日誌: 記錄執行時間超過指定時間的操做 中繼日誌： 備庫將主庫的二進制日誌複製到本身的中繼日誌中，從而在本地進行重放 通用日誌： 審計哪一個帳號、在哪一個時段、作了哪些事件 事務日誌或稱redo日誌： 記錄Innodb事務相關的如事務執行時間、檢查點等 ======================================================== 1、bin-log 1. 啓用 # vim /etc/my.cnf [mysqld] log-bin[=dir\[filename]] # service mysqld restart 2. 暫停 //僅當前會話 SET SQL_LOG_BIN=0; SET SQL_LOG_BIN=1; 3. 查看 查看所有： # mysqlbinlog mysql.000002 按時間： # mysqlbinlog mysql.000002 --start-datetime="2012-12-05 10:02:56" # mysqlbinlog mysql.000002 --stop-datetime="2012-12-05 11:02:54" # mysqlbinlog mysql.000002 --start-datetime="2012-12-05 10:02:56" --stop-datetime="2012-12-05 11:02:54" 按字節數： # mysqlbinlog mysql.000002 --start-position=260 # mysqlbinlog mysql.000002 --stop-position=260 # mysqlbinlog mysql.000002 --start-position=260 --stop-position=930 4. 截斷bin-log（產生新的bin-log文件） a. 重啓mysql服務器 b. # mysql -uroot -p123 -e 'flush logs' 5. 刪除bin-log文件 # mysql -uroot -p123 -e 'reset master' 2、查詢日誌 啓用通用查詢日誌 # vim /etc/my.cnf [mysqld] log[=dir\[filename]] # service mysqld restart 3、慢查詢日誌 啓用慢查詢日誌 # vim /etc/my.cnf [mysqld] log-slow-queries[=dir\[filename]] long_query_time=n # service mysqld restart MySQL 5.6: slow-query-log=1 slow-query-log-file=slow.log long_query_time=3 查看慢查詢日誌 測試:BENCHMARK(count,expr) SELECT BENCHMARK(50000000,2*3);
第5章 MySQL之數據備份、pymysql模塊
5.1 pymysql模塊
#安裝 pip3 install pymysql
5.1.1 鏈接、執行sql、關閉（遊標）
import pymysql user=input('用戶名: ').strip() pwd=input('密碼: ').strip() #連接 conn=pymysql.connect(host='localhost',user='root',password='123',database='egon',charset='utf8') #遊標 cursor=conn.cursor() #執行完畢返回的結果集默認以元組顯示 #cursor=conn.cursor(cursor=pymysql.cursors.DictCursor) #執行sql語句 sql='select * from userinfo where name="%s" and password="%s"' %(user,pwd) #注意%s須要加引號 print(sql) res=cursor.execute(sql) #執行sql語句，返回sql查詢成功的記錄數目 print(res) cursor.close() conn.close() if res: print('登陸成功') else: print('登陸失敗')
5.1.2 execute()之sql注入問題
注意：符號--會註釋掉它以後的sql，正確的語法：--後至少有一個任意字符
根本原理：就根據程序的字符串拼接name='%s'，咱們輸入一個xxx' -- haha,用咱們輸入的xxx加'在程序中拼接成一個判斷條件name='xxx' -- haha'
最後那一個空格，在一條sql語句中若是遇到select * from t1 where id > 3 -- and name='egon';則--以後的條件被註釋掉了 #一、sql注入之：用戶存在，繞過密碼 egon' -- 任意字符
#二、sql注入之：用戶不存在，繞過用戶與密碼 xxx' or 1=1 -- 任意字符
解決方法：
# 原來是咱們對sql進行字符串拼接 # sql="select * from userinfo where name='%s' and password='%s'" %(user,pwd) # print(sql) # res=cursor.execute(sql) #改寫爲（execute幫咱們作字符串拼接，咱們無需且必定不能再爲%s加引號了） sql="select * from userinfo where name=%s and password=%s" #！！！注意%s須要去掉引號，由於pymysql會自動爲咱們加上 res=cursor.execute(sql,[user,pwd]) #pymysql模塊自動幫咱們解決sql注入的問題，只要咱們按照pymysql的規矩來。
5.1.3 增、刪、改：conn.commit()
import pymysql #連接 conn=pymysql.connect(host='localhost',user='root',password='123',database='egon') #遊標 cursor=conn.cursor() #執行sql語句 #part1 # sql='insert into userinfo(name,password) values("root","123456");' # res=cursor.execute(sql) #執行sql語句，返回sql影響成功的行數 # print(res) #part2 # sql='insert into userinfo(name,password) values(%s,%s);' # res=cursor.execute(sql,("root","123456")) #執行sql語句，返回sql影響成功的行數 # print(res) #part3 sql='insert into userinfo(name,password) values(%s,%s);' res=cursor.executemany(sql,[("root","123456"),("lhf","12356"),("eee","156")]) #執行sql語句，返回sql影響成功的行數 print(res) conn.commit() #提交後才發現表中插入記錄成功 cursor.close() conn.close()
5.1.4 查：fetchone，fetchmany，fetchall
import pymysql #連接 conn=pymysql.connect(host='localhost',user='root',password='123',database='egon') #遊標 cursor=conn.cursor() #執行sql語句 sql='select * from userinfo;' rows=cursor.execute(sql) #執行sql語句，返回sql影響成功的行數rows,將結果放入一個集合，等待被查詢 # cursor.scroll(3,mode='absolute') # 相對絕對位置移動 # cursor.scroll(3,mode='relative') # 相對當前位置移動 res1=cursor.fetchone() res2=cursor.fetchone() res3=cursor.fetchone() res4=cursor.fetchmany(2) res5=cursor.fetchall() print(res1) print(res2) print(res3) print(res4) print(res5) print('%s rows in set (0.00 sec)' %rows) conn.commit() #提交後才發現表中插入記錄成功 cursor.close() conn.close() ''' (1, 'root', '123456') (2, 'root', '123456') (3, 'root', '123456') ((4, 'root', '123456'), (5, 'root', '123456')) ((6, 'root', '123456'), (7, 'lhf', '12356'), (8, 'eee', '156')) rows in set (0.00 sec) '''
5.1.5 獲取插入的最後一條數據的自增ID
import pymysql conn=pymysql.connect(host='localhost',user='root',password='123',database='egon') cursor=conn.cursor() sql='insert into userinfo(name,password) values("xxx","123");' rows=cursor.execute(sql) print(cursor.lastrowid) #在插入語句後查看 conn.commit() cursor.close() conn.close()
5.1.6 課堂實例講解
#一、基本使用 # ''' # create table user( # id int primary key auto_increment, # username char(16), # password char(20) # ); # insert into user(username,password) values # ('egon','123'), # ('alex','456'), # ('wxx','456'); # ''' # # import pymysql # # user=input('user>>: ').strip() # pwd=input('password>>: ').strip() # # #一、建鏈接 # conn=pymysql.connect( # host='127.0.0.1', # port=3306, # user='root', # password='123', # db='db6' # ) # #二、拿遊標 # cursor=conn.cursor() # # #三、提交sql # # sql='select id from user where username="%s" and password="%s"' %(user,pwd) # # print(sql) # sql='select id from user where username=%s and password=%s' # rows=cursor.execute(sql,(user,pwd)) # # if rows: # print('登陸成功') # else: # print('用戶名或密碼錯誤') # # conn.commit() # #四、回收資源 # cursor.close() # conn.close() #二、增刪改 # import pymysql # # #一、建鏈接 # conn=pymysql.connect( # host='127.0.0.1', # port=3306, # user='root', # password='123', # db='db6' # ) # #二、拿遊標 # cursor=conn.cursor() # # #三、提交sql # sql='insert into user(username,password) values(%s,%s)' # # rows=cursor.execute(sql,('yxx','123')) # # print(rows) # # rows=cursor.executemany(sql,[('yxx1','123'),('yxx2','123'),('yxx3','123')]) # print(rows) # # # conn.commit() # #四、回收資源 # cursor.close() # conn.close() #三、查 import pymysql #一、建鏈接 conn=pymysql.connect( host='127.0.0.1', port=3306, user='root', password='123', db='db6' ) #二、拿遊標 cursor=conn.cursor(pymysql.cursors.DictCursor) #三、提交sql sql='select * from user' rows=cursor.execute(sql) # print(rows) # print(cursor.fetchall()) # print('===>',cursor.fetchall()) print(cursor.fetchone()) print(cursor.fetchone()) print(cursor.fetchmany(3)) cursor.scroll(0,mode='absolute') # 相對絕對位置移動 print(cursor.fetchone()) # cursor.scroll(3,mode='relative') # 相對當前位置移動 #四、回收資源 cursor.close() conn.close()
5.2 MySQL數據備份
#1. 物理備份： 直接複製數據庫文件，適用於大型數據庫環境。但不能恢復到異構系統中如Windows。
#2. 邏輯備份： 備份的是建表、建庫、插入等操做所執行SQL語句，適用於中小型數據庫，效率相對較低。
#3. 導出表： 將表導入到文本文件中。
5.2.1 使用mysqldump實現邏輯備份
#語法： # mysqldump -h 服務器 -u用戶名 -p密碼 數據庫名 > 備份文件.sql #示例： #單庫備份 mysqldump -uroot -p123 db1 > db1.sql mysqldump -uroot -p123 db1 table1 table2 > db1-table1-table2.sql #多庫備份 mysqldump -uroot -p123 --databases db1 db2 mysql db3 > db1_db2_mysql_db3.sql #備份全部庫 mysqldump -uroot -p123 --all-databases > all.sql
5.2.2 恢復邏輯備份
#方法一： [root@egon backup]# mysql -uroot -p123 < /backup/all.sql #方法二： mysql> use db1; mysql> SET SQL_LOG_BIN=0; mysql> source /root/db1.sql #注：若是備份/恢復單個庫時，能夠修改sql文件 DROP database if exists school; create database school; use school;
5.2.3 備份/恢復案例
#數據庫備份/恢復實驗一：數據庫損壞 備份： 1. # mysqldump -uroot -p123 --all-databases > /backup/`date +%F`_all.sql 2. # mysql -uroot -p123 -e 'flush logs' //截斷併產生新的binlog 3. 插入數據 //模擬服務器正常運行 4. mysql> set sql_log_bin=0; //模擬服務器損壞 mysql> drop database db; 恢復： 1. # mysqlbinlog 最後一個binlog > /backup/last_bin.log 2. mysql> set sql_log_bin=0; mysql> source /backup/2014-02-13_all.sql //恢復最近一次徹底備份 mysql> source /backup/last_bin.log //恢復最後個binlog文件 #數據庫備份/恢復實驗二：若是有誤刪除 備份： 1. mysqldump -uroot -p123 --all-databases > /backup/`date +%F`_all.sql 2. mysql -uroot -p123 -e 'flush logs' //截斷併產生新的binlog 3. 插入數據 //模擬服務器正常運行 4. drop table db1.t1 //模擬誤刪除 5. 插入數據 //模擬服務器正常運行 恢復： 1. # mysqlbinlog 最後一個binlog --stop-position=260 > /tmp/1.sql # mysqlbinlog 最後一個binlog --start-position=900 > /tmp/2.sql 2. mysql> set sql_log_bin=0; mysql> source /backup/2014-02-13_all.sql //恢復最近一次徹底備份 mysql> source /tmp/1.log //恢復最後個binlog文件 mysql> source /tmp/2.log //恢復最後個binlog文件 注意事項： 1. 徹底恢復到一個乾淨的環境（例如新的數據庫或刪除原有的數據庫） 2. 恢復期間全部SQL語句不該該記錄到binlog中
5.2.4 實現自動化備份
備份計劃： 1. 什麼時間 2:00 2. 對哪些數據庫備份 3. 備份文件放的位置 備份腳本： [root@egon ~]# vim /mysql_back.sql #!/bin/bash back_dir=/backup back_file=`date +%F`_all.sql user=root pass=123 if [ ! -d /backup ];then mkdir -p /backup fi # 備份並截斷日誌 mysqldump -u${user} -p${pass} --events --all-databases > ${back_dir}/${back_file} mysql -u${user} -p${pass} -e 'flush logs' # 只保留最近一週的備份 cd $back_dir find . -mtime +7 -exec rm -rf {} \; 手動測試： [root@egon ~]# chmod a+x /mysql_back.sql [root@egon ~]# chattr +i /mysql_back.sql [root@egon ~]# /mysql_back.sql 配置cron： [root@egon ~]# crontab -l * * * /mysql_back.sql
5.2.5 表的導出和導入
SELECT... INTO OUTFILE 導出文本文件 示例： mysql> SELECT * FROM school.student1 INTO OUTFILE 'student1.txt' FIELDS TERMINATED BY ',' //定義字段分隔符 OPTIONALLY ENCLOSED BY '」' //定義字符串使用什麼符號括起來 LINES TERMINATED BY '\n' ; //定義換行符 mysql 命令導出文本文件 示例: # mysql -u root -p123 -e 'select * from student1.school' > /tmp/student1.txt # mysql -u root -p123 --xml -e 'select * from student1.school' > /tmp/student1.xml # mysql -u root -p123 --html -e 'select * from student1.school' > /tmp/student1.html LOAD DATA INFILE 導入文本文件 mysql> DELETE FROM student1; mysql> LOAD DATA INFILE '/tmp/student1.txt' INTO TABLE school.student1 FIELDS TERMINATED BY ',' OPTIONALLY ENCLOSED BY '」' LINES TERMINATED BY '\n';
####################報錯：Variable 'secure_file_priv' is a read only################## #可能會報錯 mysql> select * from db1.emp into outfile 'C:\\db1.emp.txt' fields terminated by ',' lines terminated by '\r\n'; ERROR 1238 (HY000): Variable 'secure_file_priv' is a read only variable #數據庫最關鍵的是數據，一旦數據庫權限泄露，那麼經過上述語句就能夠輕鬆將數據導出到文件中而後下載拿走，於是mysql對此做了限制，只能將文件導出到指定目錄 在配置文件中 [mysqld] secure_file_priv='C:\\' #只能將數據導出到C:\\下 重啓mysql 從新執行上述語句
5.2.6 數據庫遷移
務必保證在相同版本之間遷移
# mysqldump -h 源IP -uroot -p123 --databases db1 | mysql -h 目標IP -uroot -p456
第6章 MySQL之觸發器、事務、存儲過程、函數
6.1 觸發器
使用觸發器能夠定製用戶對錶進行【增、刪、改】操做時先後的行爲，注意：沒有查詢
6.1.1 建立觸發器
# 插入前 CREATE TRIGGER tri_before_insert_tb1 BEFORE INSERT ON tb1 FOR EACH ROW BEGIN ... END # 插入後 CREATE TRIGGER tri_after_insert_tb1 AFTER INSERT ON tb1 FOR EACH ROW BEGIN ... END # 刪除前 CREATE TRIGGER tri_before_delete_tb1 BEFORE DELETE ON tb1 FOR EACH ROW BEGIN ... END # 刪除後 CREATE TRIGGER tri_after_delete_tb1 AFTER DELETE ON tb1 FOR EACH ROW BEGIN ... END # 更新前 CREATE TRIGGER tri_before_update_tb1 BEFORE UPDATE ON tb1 FOR EACH ROW BEGIN ... END # 更新後 CREATE TRIGGER tri_after_update_tb1 AFTER UPDATE ON tb1 FOR EACH ROW BEGIN ... END
#####################插入後觸發觸發器########################## #準備表 CREATE TABLE cmd ( id INT PRIMARY KEY auto_increment, USER CHAR (32), priv CHAR (10), cmd CHAR (64), sub_time datetime, #提交時間 success enum ('yes', 'no') #0表明執行失敗 ); CREATE TABLE errlog ( id INT PRIMARY KEY auto_increment, err_cmd CHAR (64), err_time datetime ); #建立觸發器 delimiter // CREATE TRIGGER tri_after_insert_cmd AFTER INSERT ON cmd FOR EACH ROW BEGIN IF NEW.success = 'no' THEN #等值判斷只有一個等號 INSERT INTO errlog(err_cmd, err_time) VALUES(NEW.cmd, NEW.sub_time) ; #必須加分號 END IF ; #必須加分號 END// delimiter ; #往表cmd中插入記錄，觸發觸發器，根據IF的條件決定是否插入錯誤日誌 INSERT INTO cmd ( USER, priv, cmd, sub_time, success ) VALUES ('egon','0755','ls -l /etc',NOW(),'yes'), ('egon','0755','cat /etc/passwd',NOW(),'no'), ('egon','0755','useradd xxx',NOW(),'no'), ('egon','0755','ps aux',NOW(),'yes'); #查詢錯誤日誌，發現有兩條 mysql> select * from errlog; +----+-----------------+---------------------+ | id | err_cmd | err_time | +----+-----------------+---------------------+ | 1 | cat /etc/passwd | 2017-09-14 22:18:48 | | 2 | useradd xxx | 2017-09-14 22:18:48 | +----+-----------------+---------------------+ rows in set (0.00 sec)
特別的：NEW表示即將插入的數據行，OLD表示即將刪除的數據行。
6.1.2 使用觸發器
觸發器沒法由用戶直接調用，而知因爲對錶的【增/刪/改】操做被動引起的。
6.1.3 刪除觸發器
drop trigger tri_after_insert_cmd;
6.2 事務
事務用於將某些操做的多個SQL做爲原子性操做，一旦有某一個出現錯誤，便可回滾到原來的狀態，從而保證數據庫數據完整性。
create table user( id int primary key auto_increment, name char(32), balance int ); insert into user(name,balance) values ('wsb',1000), ('egon',1000), ('ysb',1000); #原子操做 start transaction; update user set balance=900 where name='wsb'; #買支付100元 update user set balance=1010 where name='egon'; #中介拿走10元 update user set balance=1090 where name='ysb'; #賣家拿到90元 commit; #出現異常，回滾到初始狀態 start transaction; update user set balance=900 where name='wsb'; #買支付100元 update user set balance=1010 where name='egon'; #中介拿走10元 uppdate user set balance=1090 where name='ysb'; #賣家拿到90元,出現異常沒有拿到 rollback; commit; mysql> select * from user; +----+------+---------+ | id | name | balance | +----+------+---------+ | 1 | wsb | 1000 | | 2 | egon | 1000 | | 3 | ysb | 1000 | +----+------+---------+ rows in set (0.00 sec)
6.3 存儲過程
6.3.1 介紹
存儲過程包含了一系列可執行的sql語句，存儲過程存放於MySQL中，經過調用它的名字能夠執行其內部的一堆sql
使用存儲過程的優勢：
#1. 用於替代程序寫的SQL語句，實現程序與sql解耦
#2. 基於網絡傳輸，傳別名的數據量小，而直接傳sql數據量大
使用存儲過程的缺點：
#1. 程序員擴展功能不方便
補充：程序與數據庫結合使用的三種方式
#方式一： MySQL：存儲過程 程序：調用存儲過程 #方式二： MySQL： 程序：純SQL語句 #方式三： MySQL: 程序：類和對象，即ORM（本質仍是純SQL語句）
6.3.2 建立簡單存儲過程（無參）
delimiter // create procedure p1() BEGIN select * from blog; INSERT into blog(name,sub_time) values("xxx",now()); END // delimiter ; #在mysql中調用 call p1() #在python中基於pymysql調用 cursor.callproc('p1') print(cursor.fetchall())
6.3.3 建立存儲過程（有參）
對於存儲過程，能夠接收參數，其參數有三類： #in 僅用於傳入參數用 #out 僅用於返回值用 #inout 既能夠傳入又能夠看成返回值
#############################in:傳入參數############################### delimiter // create procedure p2( in n1 int, in n2 int ) BEGIN select * from blog where id > n1; END // delimiter ; #在mysql中調用 call p2(3,2) #在python中基於pymysql調用 cursor.callproc('p2',(3,2)) print(cursor.fetchall())
##########################out：返回值############################# delimiter // create procedure p3( in n1 int, out res int ) BEGIN select * from blog where id > n1; set res = 1; END // delimiter ; #在mysql中調用 set @res=0; #0表明假（執行失敗），1表明真（執行成功） call p3(3,@res); select @res; #在python中基於pymysql調用 cursor.callproc('p3',(3,0)) #0至關於set @res=0 print(cursor.fetchall()) #查詢select的查詢結果 cursor.execute('select @_p3_0,@_p3_1;') #@p3_0表明第一個參數，@p3_1表明第二個參數，即返回值 print(cursor.fetchall())
#######################inout:既能夠傳入又能夠返回########################### delimiter // create procedure p4( inout n1 int ) BEGIN select * from blog where id > n1; set n1 = 1; END // delimiter ; #在mysql中調用 set @x=3; call p4(@x); select @x; #在python中基於pymysql調用 cursor.callproc('p4',(3,)) print(cursor.fetchall()) #查詢select的查詢結果 cursor.execute('select @_p4_0;') print(cursor.fetchall())
#############################事務################################## #介紹 delimiter // create procedure p4( out status int ) BEGIN 1. 聲明若是出現異常則執行{ set status = 1; rollback; } 開始事務 -- 由秦兵帳戶減去100 -- 方少偉帳戶加90 -- 張根帳戶加10 commit; 結束 set status = 2; END // delimiter ; #實現 delimiter // create PROCEDURE p5( OUT p_return_code tinyint ) BEGIN DECLARE exit handler for sqlexception BEGIN -- ERROR set p_return_code = 1; rollback; END; DECLARE exit handler for sqlwarning BEGIN -- WARNING set p_return_code = 2; rollback; END; START TRANSACTION; DELETE from tb1; #執行失敗 insert into blog(name,sub_time) values('yyy',now()); COMMIT; -- SUCCESS set p_return_code = 0; #0表明執行成功 END // delimiter ; #在mysql中調用存儲過程 set @res=123; call p5(@res); select @res; #在python中基於pymysql調用存儲過程 cursor.callproc('p5',(123,)) print(cursor.fetchall()) #查詢select的查詢結果 cursor.execute('select @_p5_0;') print(cursor.fetchall())
6.3.4 執行存儲過程
############################在MySQL中執行存儲過程############################## -- 無參數 call proc_name() -- 有參數，全in call proc_name(1,2) -- 有參數，有in，out，inout set @t1=0; set @t2=3; call proc_name(1,2,@t1,@t2) 執行存儲過程
#########################在python中基於pymysql執行存儲過程########################### #!/usr/bin/env python # -*- coding:utf-8 -*- import pymysql conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1') cursor = conn.cursor(cursor=pymysql.cursors.DictCursor) # 執行存儲過程 cursor.callproc('p1', args=(1, 22, 3, 4)) # 獲取執行完存儲的參數 cursor.execute("select @_p1_0,@_p1_1,@_p1_2,@_p1_3") result = cursor.fetchall() conn.commit() cursor.close() conn.close() print(result)
6.3.5 刪除存儲過程
drop procedure proc_name;
6.3.6 課堂實例
''' delimiter // create procedure p1() BEGIN select user,host from mysql.user; END // delimiter ; delimiter // create procedure p2( in n1 int, in n2 int, out n3 int ) BEGIN select * from emp where id > n1 and id < n2; set n3=1; END // delimiter ; ''' import pymysql #一、建鏈接 conn=pymysql.connect( host='127.0.0.1', port=3306, user='root', password='123', db='db5' ) #二、拿遊標 cursor=conn.cursor(pymysql.cursors.DictCursor) #三、提交sql # cursor.callproc('p1') # print(cursor.fetchall()) cursor.callproc('p2',(3,5,0)) #@_p2_0=3,@_p2_1=5,@_p2_2=0 print(cursor.fetchall()) cursor.execute('select @_p2_2') print(cursor.fetchone()) #四、回收資源 cursor.close() conn.close()
6.4 函數
MySQL中提供了許多內置函數，例如：
1、數學函數 ROUND(x,y) 返回參數x的四捨五入的有y位小數的值 RAND() 返回０到１內的隨機值,能夠經過提供一個參數(種子)使RAND()隨機數生成器生成一個指定的值。 2、聚合函數(經常使用於GROUP BY從句的SELECT查詢中) AVG(col)返回指定列的平均值 COUNT(col)返回指定列中非NULL值的個數 MIN(col)返回指定列的最小值 MAX(col)返回指定列的最大值 SUM(col)返回指定列的全部值之和 GROUP_CONCAT(col) 返回由屬於一組的列值鏈接組合而成的結果 3、字符串函數 CHAR_LENGTH(str) 返回值爲字符串str 的長度，長度的單位爲字符。一個多字節字符算做一個單字符。 CONCAT(str1,str2,...) 字符串拼接 若有任何一個參數爲NULL ，則返回值爲 NULL。 CONCAT_WS(separator,str1,str2,...) 字符串拼接（自定義鏈接符） CONCAT_WS()不會忽略任何空字符串。 (然而會忽略全部的 NULL）。 CONV(N,from_base,to_base) 進制轉換 例如： SELECT CONV('a',16,2); 表示將 a 由16進制轉換爲2進制字符串表示 FORMAT(X,D) 將數字X 的格式寫爲'#,###,###.##',以四捨五入的方式保留小數點後 D 位， 並將結果以字符串的形式返回。若 D 爲 0, 則返回結果不帶有小數點，或不含小數部分。 例如： SELECT FORMAT(12332.1,4); 結果爲： '12,332.1000' INSERT(str,pos,len,newstr) 在str的指定位置插入字符串 pos：要替換位置其實位置 len：替換的長度 newstr：新字符串 特別的： 若是pos超過原字符串長度，則返回原字符串 若是len超過原字符串長度，則由新字符串徹底替換 INSTR(str,substr) 返回字符串 str 中子字符串的第一個出現位置。 LEFT(str,len) 返回字符串str 從開始的len位置的子序列字符。 LOWER(str) 變小寫 UPPER(str) 變大寫 REVERSE(str) 返回字符串 str ，順序和字符順序相反。 SUBSTRING(str,pos) , SUBSTRING(str FROM pos) SUBSTRING(str,pos,len) , SUBSTRING(str FROM pos FOR len) 不帶有len 參數的格式從字符串str返回一個子字符串，起始於位置 pos。帶有len參數的格式從字符串str返回一個長度同len字符相同的子字符串，起始於位置 pos。 使用 FROM的格式爲標準 SQL 語法。也可能對pos使用一個負值。倘若這樣，則子字符串的位置起始於字符串結尾的pos 字符，而不是字符串的開頭位置。在如下格式的函數中能夠對pos 使用一個負值。 mysql> SELECT SUBSTRING('Quadratically',5); -> 'ratically' mysql> SELECT SUBSTRING('foobarbar' FROM 4); -> 'barbar' mysql> SELECT SUBSTRING('Quadratically',5,6); -> 'ratica' mysql> SELECT SUBSTRING('Sakila', -3); -> 'ila' mysql> SELECT SUBSTRING('Sakila', -5, 3); -> 'aki' mysql> SELECT SUBSTRING('Sakila' FROM -4 FOR 2); -> 'ki' 4、日期和時間函數 CURDATE()或CURRENT_DATE() 返回當前的日期 CURTIME()或CURRENT_TIME() 返回當前的時間 DAYOFWEEK(date) 返回date所表明的一星期中的第幾天(1~7) DAYOFMONTH(date) 返回date是一個月的第幾天(1~31) DAYOFYEAR(date) 返回date是一年的第幾天(1~366) DAYNAME(date) 返回date的星期名，如：SELECT DAYNAME(CURRENT_DATE); FROM_UNIXTIME(ts,fmt) 根據指定的fmt格式，格式化UNIX時間戳ts HOUR(time) 返回time的小時值(0~23) MINUTE(time) 返回time的分鐘值(0~59) MONTH(date) 返回date的月份值(1~12) MONTHNAME(date) 返回date的月份名，如：SELECT MONTHNAME(CURRENT_DATE); NOW() 返回當前的日期和時間 QUARTER(date) 返回date在一年中的季度(1~4)，如SELECT QUARTER(CURRENT_DATE); WEEK(date) 返回日期date爲一年中第幾周(0~53) YEAR(date) 返回日期date的年份(1000~9999) 重點: DATE_FORMAT(date,format) 根據format字符串格式化date值 mysql> SELECT DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y'); -> 'Sunday October 2009' mysql> SELECT DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s'); -> '22:23:00' mysql> SELECT DATE_FORMAT('1900-10-04 22:23:00', -> '%D %y %a %d %m %b %j'); -> '4th 00 Thu 04 10 Oct 277' mysql> SELECT DATE_FORMAT('1997-10-04 22:23:00', -> '%H %k %I %r %T %S %w'); -> '22 22 10 10:23:00 PM 22:23:00 00 6' mysql> SELECT DATE_FORMAT('1999-01-01', '%X %V'); -> '1998 52' mysql> SELECT DATE_FORMAT('2006-06-00', '%d'); -> '00' 5、加密函數 MD5() 計算字符串str的MD5校驗和 PASSWORD(str) 返回字符串str的加密版本，這個加密過程是不可逆轉的，和UNIX密碼加密過程使用不一樣的算法。 6、控制流函數 CASE WHEN[test1] THEN [result1]...ELSE [default] END 若是testN是真，則返回resultN，不然返回default CASE [test] WHEN[val1] THEN [result]...ELSE [default]END 若是test和valN相等，則返回resultN，不然返回default IF(test,t,f) 若是test是真，返回t；不然返回f IFNULL(arg1,arg2) 若是arg1不是空，返回arg1，不然返回arg2 NULLIF(arg1,arg2) 若是arg1=arg2返回NULL；不然返回arg1 7、控制流函數小練習 #7.一、準備表 /* Navicat MySQL Data Transfer Source Server : localhost_3306 Source Server Version : 50720 Source Host : localhost:3306 Source Database : student Target Server Type : MYSQL Target Server Version : 50720 File Encoding : 65001 Date: 2018-01-02 12:05:30 */ SET FOREIGN_KEY_CHECKS=0; -- ---------------------------- -- Table structure for course -- ---------------------------- DROP TABLE IF EXISTS `course`; CREATE TABLE `course` ( `c_id` int(11) NOT NULL, `c_name` varchar(255) DEFAULT NULL, `t_id` int(11) DEFAULT NULL, PRIMARY KEY (`c_id`), KEY `t_id` (`t_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of course -- ---------------------------- INSERT INTO `course` VALUES ('1', 'python', '1'); INSERT INTO `course` VALUES ('2', 'java', '2'); INSERT INTO `course` VALUES ('3', 'linux', '3'); INSERT INTO `course` VALUES ('4', 'web', '2'); -- ---------------------------- -- Table structure for score -- ---------------------------- DROP TABLE IF EXISTS `score`; CREATE TABLE `score` ( `id` int(11) NOT NULL AUTO_INCREMENT, `s_id` int(10) DEFAULT NULL, `c_id` int(11) DEFAULT NULL, `num` double DEFAULT NULL, PRIMARY KEY (`id`) ) ENGINE=InnoDB AUTO_INCREMENT=12 DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of score -- ---------------------------- INSERT INTO `score` VALUES ('1', '1', '1', '79'); INSERT INTO `score` VALUES ('2', '1', '2', '78'); INSERT INTO `score` VALUES ('3', '1', '3', '35'); INSERT INTO `score` VALUES ('4', '2', '2', '32'); INSERT INTO `score` VALUES ('5', '3', '1', '66'); INSERT INTO `score` VALUES ('6', '4', '2', '77'); INSERT INTO `score` VALUES ('7', '4', '1', '68'); INSERT INTO `score` VALUES ('8', '5', '1', '66'); INSERT INTO `score` VALUES ('9', '2', '1', '69'); INSERT INTO `score` VALUES ('10', '4', '4', '75'); INSERT INTO `score` VALUES ('11', '5', '4', '66.7'); -- ---------------------------- -- Table structure for student -- ---------------------------- DROP TABLE IF EXISTS `student`; CREATE TABLE `student` ( `s_id` varchar(20) NOT NULL, `s_name` varchar(255) DEFAULT NULL, `s_age` int(10) DEFAULT NULL, `s_sex` char(1) DEFAULT NULL, PRIMARY KEY (`s_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of student -- ---------------------------- INSERT INTO `student` VALUES ('1', '魯班', '12', '男'); INSERT INTO `student` VALUES ('2', '貂蟬', '20', '女'); INSERT INTO `student` VALUES ('3', '劉備', '35', '男'); INSERT INTO `student` VALUES ('4', '關羽', '34', '男'); INSERT INTO `student` VALUES ('5', '張飛', '33', '女'); -- ---------------------------- -- Table structure for teacher -- ---------------------------- DROP TABLE IF EXISTS `teacher`; CREATE TABLE `teacher` ( `t_id` int(10) NOT NULL, `t_name` varchar(50) DEFAULT NULL, PRIMARY KEY (`t_id`) ) ENGINE=InnoDB DEFAULT CHARSET=utf8; -- ---------------------------- -- Records of teacher -- ---------------------------- INSERT INTO `teacher` VALUES ('1', '大王'); INSERT INTO `teacher` VALUES ('2', 'alex'); INSERT INTO `teacher` VALUES ('3', 'egon'); INSERT INTO `teacher` VALUES ('4', 'peiqi'); #7.二、統計各科各分數段人數.顯示格式:課程ID,課程名稱,[100-85],[85-70],[70-60],[ <60] select score.c_id, course.c_name, sum(CASE WHEN num BETWEEN 85 and 100 THEN 1 ELSE 0 END) as '[100-85]', sum(CASE WHEN num BETWEEN 70 and 85 THEN 1 ELSE 0 END) as '[85-70]', sum(CASE WHEN num BETWEEN 60 and 70 THEN 1 ELSE 0 END) as '[70-60]', sum(CASE WHEN num < 60 THEN 1 ELSE 0 END) as '[ <60]' from score,course where score.c_id=course.c_id GROUP BY score.c_id;
#########################須要掌握函數：date_format############################ #1 基本使用 mysql> SELECT DATE_FORMAT('2009-10-04 22:23:00', '%W %M %Y'); -> 'Sunday October 2009' mysql> SELECT DATE_FORMAT('2007-10-04 22:23:00', '%H:%i:%s'); -> '22:23:00' mysql> SELECT DATE_FORMAT('1900-10-04 22:23:00', -> '%D %y %a %d %m %b %j'); -> '4th 00 Thu 04 10 Oct 277' mysql> SELECT DATE_FORMAT('1997-10-04 22:23:00', -> '%H %k %I %r %T %S %w'); -> '22 22 10 10:23:00 PM 22:23:00 00 6' mysql> SELECT DATE_FORMAT('1999-01-01', '%X %V'); -> '1998 52' mysql> SELECT DATE_FORMAT('2006-06-00', '%d'); -> '00' #2 準備表和記錄 CREATE TABLE blog ( id INT PRIMARY KEY auto_increment, NAME CHAR (32), sub_time datetime ); INSERT INTO blog (NAME, sub_time) VALUES ('第1篇','2015-03-01 11:31:21'), ('第2篇','2015-03-11 16:31:21'), ('第3篇','2016-07-01 10:21:31'), ('第4篇','2016-07-22 09:23:21'), ('第5篇','2016-07-23 10:11:11'), ('第6篇','2016-07-25 11:21:31'), ('第7篇','2017-03-01 15:33:21'), ('第8篇','2017-03-01 17:32:21'), ('第9篇','2017-03-01 18:31:21'); #3. 提取sub_time字段的值，按照格式後的結果即"年月"來分組 SELECT DATE_FORMAT(sub_time,'%Y-%m'),COUNT(1) FROM blog GROUP BY DATE_FORMAT(sub_time,'%Y-%m'); #結果 +-------------------------------+----------+ | DATE_FORMAT(sub_time,'%Y-%m') | COUNT(1) | +-------------------------------+----------+ | 2015-03 | 2 | | 2016-07 | 4 | | 2017-03 | 3 | +-------------------------------+----------+ rows in set (0.00 sec)
6.4.1 自定義函數
#！！！注意！！！
#函數中不要寫sql語句（不然會報錯），函數僅僅只是一個功能，是一個在sql中被應用的功能
#若要想在begin...end...中寫sql，請用存儲過程
delimiter // create function f1( i1 int, i2 int) returns int BEGIN declare num int; set num = i1 + i2; return(num); END // delimiter ;
delimiter // create function f5( i int ) returns int begin declare res int default 0; if i = 10 then set res=100; elseif i = 20 then set res=200; elseif i = 30 then set res=300; else set res=400; end if; return res; end // delimiter ;
6.4.2 刪除函數
drop function func_name;
6.4.3 執行函數
# 獲取返回值 select UPPER('egon') into @res; SELECT @res; # 在查詢中使用 select f1(11,nid) ,name from tb2;
6.5 流程控制
6.5.1 條件語句
#######################if條件語句########################## delimiter // CREATE PROCEDURE proc_if () BEGIN declare i int default 0; if i = 1 THEN SELECT 1; ELSEIF i = 2 THEN SELECT 2; ELSE SELECT 7; END IF; END // delimiter ;
6.5.2 循環語句
########################while循環################################## delimiter // CREATE PROCEDURE proc_while () BEGIN DECLARE num INT ; SET num = 0 ; WHILE num < 10 DO SELECT num ; SET num = num + 1 ; END WHILE ; END // delimiter ;
################################repeat循環################################## delimiter // CREATE PROCEDURE proc_repeat () BEGIN DECLARE i INT ; SET i = 0 ; repeat select i; set i = i + 1; until i >= 5 end repeat; END // delimiter ;
###########################loop########################### BEGIN declare i int default 0; loop_label: loop set i=i+1; if i<8 then iterate loop_label; end if; if i>=10 then leave loop_label; end if; select i; end loop loop_label; END
6.6 MySQL使用工具-IDE工具介紹
生產環境仍是推薦使用mysql命令行，但爲了方便咱們測試，可使用IDE工具
下載連接：https://pan.baidu.com/s/1bpo5mqj
工具名稱navicatformysql.zip
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