Linux服務-mysql基礎篇
mysql基礎正則表達式
1. 關係型數據庫介紹
1.1 數據結構模型
數據結構模型主要有：sql
- 層次模型
- 網狀結構
- 關係模型
關係模型又分爲:數據庫
- 二維關係：row(行)，column（列）
- 數據庫管理系統：DBMS（database manager system）
- 關係數據庫管理系統（Relational database manager system）
1.2 RDBMS專業名詞
常見的關係型數據庫管理系統：express
- MySQL：MySQL，MariaDB（和MySQL是同源，RHEL7上yum源自帶），Percona-Server
- PostgreSQL：簡稱爲pgsql
- Oracle
- MSSQL
事務:多個操做被看成一個總體對待就稱爲一個事務(整個事務中的全部操做，要麼所有完成，要麼所有不完成，不可能停滯在中間某個環節。事務在執行過程當中發生錯誤，會被回滾（Rollback）到事務開始前的狀態，就像這個事務歷來沒有執行過同樣。)安全
要看一個關係型數據庫是否支持事務，須要看其是否支持並知足ACID測試服務器
ACID:ACID是事務的一個基本標準數據結構
- A：Automicity，原子性
- C：Consistency，一致性
- I：Isolation，隔離性
- D：Durability，持久性
SQL:Structure Query Language，結構化查詢語言app
約束:constraint，向數據表提供的數據要遵照的限制socket
- 主鍵約束：一個或多個字段的組合，填入的數據必須能在本表中惟一標識本行。且必須提供數據，不能爲空（NOT NULL）。一個表只能存在一個
- 唯一鍵約束：一個或多個字段的組合，填入的數據必須能在本表中惟一標識本行。容許爲空（NULL）一個表能夠存在多個
- 外鍵約束：一個表中的某字段可填入數據取決於另外一個表的主鍵已有的數據
- 檢查性約束
索引：將表中的一個或多個字段中的數據複製一份另存，而且這些數據須要按特定次序排序存儲
關係運算：
- 選擇：挑選出符合條件的行（部分行）
- 投影：挑選出須要的字段（通常是列）
- 鏈接（將兩個表相關聯）
數據抽象方式：
- 物理層：決定數據的存儲格式，即RDBMS在磁盤上如何組織文件
- 邏輯層：描述DB存儲什麼數據，以及數據間存在什麼樣的關係
- 視圖層：描述DB中的部分數據
1.3 關係型數據庫的常見組件
關係型數據庫的常見組件有：
- 數據庫：database
- 表：table，由行（row）和列（column）組成
- 索引：index
- 視圖：view
- 用戶：user
- 權限：privilege
- 存儲過程：procedure
- 存儲函數：function
- 觸發器：trigger
- 事件調度器：event scheduler
1.4 SQL語句
SQL語句有三種類型：
- DDL：Data Defination Language，數據定義語言
- DML：Data Manipulation Language，數據操縱語言
- DCL：Data Control Language，數據控制語言
| SQL語句類型 | 對應操做 |
|---|---|
| DDL | CREATE：建立 DROP:刪除 ALTER：修改 |
| DML | INSERT：向表中插入數據 DELETE：刪除表中數據 UPDATE：更新表中數據 SELECT：查詢表中數據 |
| DCL | GRANT：受權 REVOKE：移除受權 |
2. mysql安裝與配置
2.1 mysql安裝
mysql安裝方式有三種：
- 源代碼：編譯安裝
- 二進制格式的程序包：展開至特定路徑，並通過簡單配置後便可使用
- 程序包管理器管理的程序包：
1.rpm(有兩種，os Vendor，項目官方提供)
2.deb
//第一步下載mysql5.7的yum源 [root@cwh ~]# wget http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm --2019-04-22 15:04:39-- http://dev.mysql.com/get/mysql57-community-release-el7-10.noarch.rpm ... ... 2019-04-22 15:04:46 (389 KB/s) - 已保存 「mysql57-community-release-el7-10.noarch.rpm」 [25548/25548]) [root@cwh ~]# ls aaa anaconda-ks.cfg cwh4http.sh httpd.conf httpd-vhosts.conf httppz1.sh mysql57-community-release-el7-10.noarch.rpm //第二步安裝下載下來的mysql源 [root@cwh ~]# yum -y install mysql57-community-release-el7-10.noarch.rpm [root@cwh ~]# ls /etc/yum.repos.d/ 7CentOS-Base.repo mysql-community.repo mysql-community-source.repo redhat.repo //第三步安裝mysql5.7 yum -y install mysql-community-server mysql-community-client mysql-community-common mysql-community-devel
2.2 mysql基本配置
//第一步啓動mysql並查看端口是否開啓 [root@cwh ~]# systemctl start mysqld [root@cwh ~]# ss -antl State Recv-Q Send-Q Local Address:Port Peer Address:Port LISTEN 0 128 *:22 *:* LISTEN 0 100 127.0.0.1:25 *:* LISTEN 0 80 :::3306 :::* LISTEN 0 128 :::22 :::* LISTEN 0 100 ::1:25 :::* //第二步在mysql日誌文件中找出mysql臨時密碼 [root@cwh ~]# cat /var/log/mysqld.log |grep password 2019-04-22T07:40:39.531315Z 1 [Note] A temporary password is generated for root@localhost: xB>aDF_l>4>; //最後的xB>aDF_l>4>;爲臨時密碼之後登錄時須要 //第三步使用獲取到的臨時密碼登陸mysql [root@localhost ~]# mysql -uroot -p Enter password: Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 2 Server version: 5.7.25 Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved. Oracle is a registered trademark of Oracle Corporation and/or its affiliates. Other names may be trademarks of their respective owners. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. mysql> //這樣顯示出來了就表示臨時登陸成功 //第四步修改mysql登陸密碼 mysql> set global validate_password_policy=0; Query OK, 0 rows affected (0.00 sec) mysql> set global validate_password_length=1; Query OK, 0 rows affected (0.00 sec) mysql> ALTER USER 'root'@'localhost' IDENTIFIED BY 'cwh123!'; Query OK, 0 rows affected (0.00 sec) mysql> quit Bye //第五步爲避免mysql自動升級，這裏須要卸載最開始安裝的yum源 [root@localhost ~]# rpm -qa |grep mysql mysql-community-common-5.7.25-1.el7.x86_64 mysql-community-libs-5.7.25-1.el7.x86_64 mysql-community-libs-compat-5.7.25-1.el7.x86_64 mysql-community-server-5.7.25-1.el7.x86_64 mysql57-community-release-el7-10.noarch mysql-community-client-5.7.25-1.el7.x86_64 mysql-community-devel-5.7.25-1.el7.x86_64 [root@localhost ~]# yum -y remove mysql57-community-release-el7-10.noarch
3. mysql的程序組成
- 客戶端
- mysql：CLI交互式客戶端程序
- mysql_secure_installation：安全初始化，強烈建議安裝完之後執行此命令
- mysqldump：mysql備份工具
- mysqladmin
- 服務器端
- mysqld
3.1 mysql工具使用
//語法：mysql [OPTIONS] [database]
//經常使用的OPTIONS：
-uUSERNAME //指定用戶名，默認爲root
-hHOST //指定服務器主機，默認爲localhost，推薦使用ip地址
-pPASSWORD //指定用戶的密碼
-P# //指定數據庫監聽的端口，這裏的#需用實際的端口號代替，如-P3307
-V //查看當前使用的mysql版本
-e //不登陸mysql執行sql語句後退出，經常使用於腳本
//查看當前使用的mysql腳本
[root@localhost ~]# mysql -V
mysql Ver 14.14 Distrib 5.7.25, for Linux (x86_64) using EditLine wrapper
//本地登陸
[root@cwh ~]# mysql -uroot -pcwh123! -h127.0.0.1
mysql: [Warning] Using a password on the command line interface can be insecure.
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 13
Server version: 5.7.25 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql> //此時顯示已經登錄上了
//注意，不推薦直接在命令行裏直接用-pPASSWORD的方式登陸，而是使用-p選項，而後交互式輸入密碼
[root@cwh ~]# mysql -uroot -p -h127.0.0.1
Enter password:
Welcome to the MySQL monitor. Commands end with ; or \g.
Your MySQL connection id is 14
Server version: 5.7.25 MySQL Community Server (GPL)
Copyright (c) 2000, 2019, Oracle and/or its affiliates. All rights reserved.
Oracle is a registered trademark of Oracle Corporation and/or its
affiliates. Other names may be trademarks of their respective
owners.
Type 'help;' or '\h' for help. Type '\c' to clear the current input statement.
mysql>
//查看mysql中有哪些數據庫
[root@localhost ~]# mysql -uroot -p -h127.0.0.1 -e 'show databases'
Enter password:
+--------------------+
| Database |
+--------------------+
| information_schema |
| mysql |
| performance_schema |
| sys |
+--------------------+
3.2 服務器監聽的兩種socket地址
| socket類型 | 說明 |
|---|---|
| ip socket | 默認監聽在tcp的3306端口，支持遠程通訊 |
| unix sock | 監聽在sock文件上（/tmp/mysql.sock，/var/lib/mysql/mysql.sock 僅支持本地通訊 server地址只能是：localhost，127.0.0.1 |
4. mysql數據庫操做
4.1 DDL操做
4.1.1 數據庫操做
//建立數據庫 //語法：CREATE DATABASE [IF NOT EXISTS] 'DB_NAME'; //建立數據庫chengweihong [root@localhost ~]# mysql -uroot -p Enter password: mysql> mysql> create database if not exists chengweihong; Query OK, 1 row affected (0.00 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | chengweihong | | mysql | | performance_schema | | sys | +--------------------+ 5 rows in set (0.00 sec) //刪除數據庫 //語法：DROP DATABASE [IF EXISTS] 'DB_NAME'; //刪除數據庫chengweihong mysql> drop database if exists chengweihong; Query OK, 0 rows affected (0.02 sec) mysql> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | mysql | | performance_schema | | sys | +--------------------+ 4 rows in set (0.00 sec)
4.1.2 表操做
//建立表 //語法：CREATE TABLE table_name (col1 datatype 修飾符,col2 datatype 修飾符) ENGINE='存儲引擎類型'; //在數據庫chengweihong裏建立表cwh //首先建立chengweihong數據庫 mysql> create database chengweihong; Query OK, 1 row affected (0.01 sec) //在在數據庫chengweihong中建立表 mysql> create table cwh(id int not null,name varchar(100),age tinyint); Query OK, 0 rows affected (0.04 sec) mysql> show tables; +------------------------+ | Tables_in_chengweihong | +------------------------+ | cwh | +------------------------+ 1 row in set (0.00 sec) //具體查看錶的內容 mysql> desc cwh; +-------+--------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +-------+--------------+------+-----+---------+-------+ | id | int(11) | NO | | NULL | | | name | varchar(100) | YES | | NULL | | | age | tinyint(4) | YES | | NULL | | +-------+--------------+------+-----+---------+-------+ 3 rows in set (0.03 sec) //刪除表 //語法：DROP TABLE [ IF EXISTS ] 'table_name'; //刪除表cwh mysql> drop table if exists cwh; Query OK, 0 rows affected (0.01 sec) mysql> show tables; Empty set (0.00 sec)
4.1.3 用戶操做
mysql用戶賬號由兩部分組成,如'USERNAME'@'HOST'，表示此USERNAME只能今後HOST上遠程登陸
這裏（'USERNAME'@'HOST'）的HOST用於限制此用戶可經過哪些主機遠程鏈接mysql程序，其值可爲:
- IP地址，如：172.16.12.129
- 通配符
- %：匹配任意長度的任意字符，經常使用於設置容許從任何主機登陸
- _：匹配任意單個字符
//數據庫用戶建立 //語法：CREATE USER 'username'@'host' [IDENTIFIED BY 'password']; //建立數據庫用戶wangqing mysql> create user cwh@192.168.112.149 identified by 'cwh123!'; Query OK, 0 rows affected (0.01 sec) //在192.168.112.149上驗證 [root@149 ~]# mysql -ucwh -p -h192.168.112.146 Enter password: Welcome to the MariaDB monitor. Commands end with ; or \g. Your MySQL connection id is 19 Server version: 5.7.25 MySQL Community Server (GPL) Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MySQL [(none)]> //由於沒有配置權限因此查看的東西有限，看不到chengweihong的數據庫 MySQL [(none)]> show databases; +--------------------+ | Database | +--------------------+ | information_schema | +--------------------+ 1 row in set (0.01 sec) //刪除數據庫用戶 //語法：DROP USER 'username'@'host'; mysql> drop user cwh@192.168.112.149; Query OK, 0 rows affected (0.01 sec) //刪除用戶後在192.168.112.149主機上驗證 [root@149 ~]# mysql -ucwh -p -h192.168.112.146 Enter password: ERROR 1130 (HY000): Host '192.168.112.149' is not allowed to connect to this MySQL server //能夠看出已經沒法登錄了
4.1.4 查看命令SHOW
//1.查看有哪些數據庫
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
| chengweihong |
| mysql |
| performance_schema |
| sys |
+--------------------+
5 rows in set (0.00 sec)
//2.查看數據庫中有哪些表格（要看那個數據的表格就先進入到數據庫中）
mysql> use chengweihong
Database changed
mysql> show tables;
+------------------------+
| Tables_in_chengweihong |
+------------------------+
| cwh |
+------------------------+
1 row in set (0.00 sec)
//3.查看支持的全部字符集
mysql> show character set;
+----------+---------------------------------+---------------------+--------+
| Charset | Description | Default collation | Maxlen |
+----------+---------------------------------+---------------------+--------+
| big5 | Big5 Traditional Chinese | big5_chinese_ci | 2 |
| dec8 | DEC West European | dec8_swedish_ci | 1 |
| cp850 | DOS West European | cp850_general_ci | 1 |
| hp8 | HP West European | hp8_english_ci | 1 |
| koi8r | KOI8-R Relcom Russian | koi8r_general_ci | 1 |
| latin1 | cp1252 West European | latin1_swedish_ci | 1 |
| latin2 | ISO 8859-2 Central European | latin2_general_ci | 1 |
| swe7 | 7bit Swedish | swe7_swedish_ci | 1 |
| ascii | US ASCII | ascii_general_ci | 1 |
| ujis | EUC-JP Japanese | ujis_japanese_ci | 3 |
| sjis | Shift-JIS Japanese | sjis_japanese_ci | 2 |
| hebrew | ISO 8859-8 Hebrew | hebrew_general_ci | 1 |
| tis620 | TIS620 Thai | tis620_thai_ci | 1 |
| euckr | EUC-KR Korean | euckr_korean_ci | 2 |
| koi8u | KOI8-U Ukrainian | koi8u_general_ci | 1 |
| gb2312 | GB2312 Simplified Chinese | gb2312_chinese_ci | 2 |
| greek | ISO 8859-7 Greek | greek_general_ci | 1 |
| cp1250 | Windows Central European | cp1250_general_ci | 1 |
| gbk | GBK Simplified Chinese | gbk_chinese_ci | 2 |
| latin5 | ISO 8859-9 Turkish | latin5_turkish_ci | 1 |
| armscii8 | ARMSCII-8 Armenian | armscii8_general_ci | 1 |
| utf8 | UTF-8 Unicode | utf8_general_ci | 3 |
| ucs2 | UCS-2 Unicode | ucs2_general_ci | 2 |
| cp866 | DOS Russian | cp866_general_ci | 1 |
| keybcs2 | DOS Kamenicky Czech-Slovak | keybcs2_general_ci | 1 |
| macce | Mac Central European | macce_general_ci | 1 |
| macroman | Mac West European | macroman_general_ci | 1 |
| cp852 | DOS Central European | cp852_general_ci | 1 |
| latin7 | ISO 8859-13 Baltic | latin7_general_ci | 1 |
| utf8mb4 | UTF-8 Unicode | utf8mb4_general_ci | 4 |
| cp1251 | Windows Cyrillic | cp1251_general_ci | 1 |
| utf16 | UTF-16 Unicode | utf16_general_ci | 4 |
| utf16le | UTF-16LE Unicode | utf16le_general_ci | 4 |
| cp1256 | Windows Arabic | cp1256_general_ci | 1 |
| cp1257 | Windows Baltic | cp1257_general_ci | 1 |
| utf32 | UTF-32 Unicode | utf32_general_ci | 4 |
| binary | Binary pseudo charset | binary | 1 |
| geostd8 | GEOSTD8 Georgian | geostd8_general_ci | 1 |
| cp932 | SJIS for Windows Japanese | cp932_japanese_ci | 2 |
| eucjpms | UJIS for Windows Japanese | eucjpms_japanese_ci | 3 |
| gb18030 | China National Standard GB18030 | gb18030_chinese_ci | 4 |
+----------+---------------------------------+---------------------+--------+
41 rows in set (0.01 sec)
//4.查看當前數據庫支持的全部存儲引擎
mysql> show engines;
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| Engine | Support | Comment | Transactions | XA | Savepoints |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
| InnoDB | DEFAULT | Supports transactions, row-level locking, and foreign keys | YES | YES | YES |
| MRG_MYISAM | YES | Collection of identical MyISAM tables | NO | NO | NO |
| MEMORY | YES | Hash based, stored in memory, useful for temporary tables | NO | NO | NO |
| BLACKHOLE | YES | /dev/null storage engine (anything you write to it disappears) | NO | NO | NO |
| MyISAM | YES | MyISAM storage engine | NO | NO | NO |
| CSV | YES | CSV storage engine | NO | NO | NO |
| ARCHIVE | YES | Archive storage engine | NO | NO | NO |
| PERFORMANCE_SCHEMA | YES | Performance Schema | NO | NO | NO |
| FEDERATED | NO | Federated MySQL storage engine | NULL | NULL | NULL |
+--------------------+---------+----------------------------------------------------------------+--------------+------+------------+
9 rows in set (0.00 sec)
//5.不進入某數據庫而列出其包含的全部表
mysql> show tables from chengweihong;
+------------------------+
| Tables_in_chengweihong |
+------------------------+
| cwh |
+------------------------+
1 row in set (0.00 sec)
//6.查看錶結構
//語法：DESC [db_name.]table_name;
mysql> desc chengweihong.cwh;
+-------+--------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-------+--------------+------+-----+---------+-------+
| id | int(11) | NO | | NULL | |
| name | varchar(100) | YES | | NULL | |
| age | tinyint(4) | YES | | NULL | |
+-------+--------------+------+-----+---------+-------+
3 rows in set (0.00 sec)
//7.查看某表的建立命令
//語法：SHOW CREATE TABLE table_name;
mysql> show create table cwh;
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------+
| Table | Create Table |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------+
| cwh | CREATE TABLE `cwh` (
`id` int(11) NOT NULL,
`name` varchar(100) DEFAULT NULL,
`age` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 |
+-------+----------------------------------------------------------------------------------------------------------------------------------------------------------+
1 row in set (0.00 sec)
//查看某表的狀態
//語法：SHOW TABLE STATUS LIKE 'table_name'\G
mysql> show create table cwh\G;
*************************** 1. row ***************************
Table: cwh
Create Table: CREATE TABLE `cwh` (
`id` int(11) NOT NULL,
`name` varchar(100) DEFAULT NULL,
`age` tinyint(4) DEFAULT NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
4.1.5 獲取幫助
//獲取建立表的幫助
mysql> help create table
Name: 'CREATE TABLE'
Description:
Syntax:
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
(create_definition,...)
[table_options]
[partition_options]
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
[(create_definition,...)]
[table_options]
[partition_options]
[IGNORE | REPLACE]
[AS] query_expression
CREATE [TEMPORARY] TABLE [IF NOT EXISTS] tbl_name
{ LIKE old_tbl_name | (LIKE old_tbl_name) }
4.2 DML操做（數據操控語言）
DML操做包括增(INSERT)、刪(DELETE)、改(UPDATE)、查(SELECT)，均屬針對表的操做。
4.2.1 INSERT語句
1.一次插入一條完整數據
mysql> insert into cwh value(1,'tom',10); Query OK, 1 row affected (0.01 sec) mysql> select * from cwh; +----+------+------+ | id | name | age | +----+------+------+ | 1 | tom | 10 | +----+------+------+ 1 row in set (0.00 sec)
2.一次插入多條完整數據
mysql> insert into cwh values(2,'jerry',20),(3,'natasha',30)
-> ; //由於最後沒有輸入分號
Query OK, 2 rows affected (0.01 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> select * from cwh
-> ; //由於ui後沒輸入；
+----+---------+------+
| id | name | age |
+----+---------+------+
| 1 | tom | 10 |
| 2 | jerry | 20 |
| 3 | natasha | 30 |
+----+---------+------+
3 rows in set (0.00 sec)
3.一次插入一條指定字段的數據
mysql> insert into cwh(id,name) value(4,'aaa'); Query OK, 1 row affected (0.00 sec) mysql> select * from cwh; +----+---------+------+ | id | name | age | +----+---------+------+ | 1 | tom | 10 | | 2 | jerry | 20 | | 3 | natasha | 30 | | 4 | aaa | NULL | +----+---------+------+ 4 rows in set (0.00 sec)
4.一次插入多條指定字段的數據
mysql> insert into cwh(id,name) values(5,'bbb'),(6,'ccc');
Query OK, 2 rows affected (0.00 sec)
Records: 2 Duplicates: 0 Warnings: 0
mysql> select * from cwh
-> ;
+----+---------+------+
| id | name | age |
+----+---------+------+
| 1 | tom | 10 |
| 2 | jerry | 20 |
| 3 | natasha | 30 |
| 4 | aaa | NULL |
| 5 | bbb | NULL |
| 6 | ccc | NULL |
+----+---------+------+
6 rows in set (0.00 sec)
4.2.2 SELECT語句
字段column表示法
| 表示符 | 表示 |
|---|---|
| * | 全部字段 |
| as | 字段別名, 當名字很長時用別名代替 |
條件判斷語句WHERE
| 操做類型 | 經常使用操做符 |
|---|---|
| 操做符 | >，<，>=，<=，=，!= BETWEEN column# AND column# LIKE：模糊匹配 RLIKE：基於正則表達式進行模式匹配 IS NOT NULL：非空 IS NULL：空 |
| 條件邏輯操做 | AND,OR,NOT |
ORDER BY：排序，默認爲升序（ASC）
| ORDER BY語句 | 意義 |
|---|---|
| ORDER BY 'column_name' | 根據column_name進行升序排序 |
| ORDER BY 'column_name'DESC | 根據column_name進行降序排序 |
| ORDER BY ’column_name' LIMIT 2 | 根據column_name進行升序排序 並只取前2個結果 |
| ORDER BY ‘column_name' LIMIT 1,2 | 根據column_name進行升序排序而且略過第1個結果取後面的2個結果 |
//DML操做之查操做select
//語法：SELECT column1,column2,... FROM table_name [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];
1.查看錶的全部內容
mysql> select * from cwh; +----+---------+------+ | id | name | age | +----+---------+------+ | 1 | tom | 10 | | 2 | jerry | 20 | | 3 | natasha | 30 | | 4 | aaa | NULL | | 5 | bbb | NULL | | 6 | ccc | NULL | +----+---------+------+ 6 rows in set (0.00 sec)
2.按字段查看錶的內容
mysql> select name from cwh; +---------+ | name | +---------+ | tom | | jerry | | natasha | | aaa | | bbb | | ccc | +---------+ 6 rows in set (0.00 sec)
3.查看錶的內容並按某字段升序排序
mysql> select * from cwh order by age; +----+---------+------+ | id | name | age | +----+---------+------+ | 4 | aaa | NULL | | 5 | bbb | NULL | | 6 | ccc | NULL | | 1 | tom | 10 | | 2 | jerry | 20 | | 3 | natasha | 30 | +----+---------+------+ 6 rows in set (0.00 sec)
4.查看錶的內容按升序排序取前兩個
mysql> select * from cwh order by id limit 2; +----+-------+------+ | id | name | age | +----+-------+------+ | 1 | tom | 10 | | 2 | jerry | 20 | +----+-------+------+ 2 rows in set (0.00 sec)
5.查看錶的內容按升序排序跳過第一個取後兩個
mysql> select * from cwh order by id limit 1,2; +----+---------+------+ | id | name | age | +----+---------+------+ | 2 | jerry | 20 | | 3 | natasha | 30 | +----+---------+------+ 2 rows in set (0.00 sec)
6.查看錶的內容只打印age大於25的信息
mysql> select * from cwh where age >=25; +----+---------+------+ | id | name | age | +----+---------+------+ | 3 | natasha | 30 | +----+---------+------+ 1 row in set (0.00 sec)
7.查看錶的內容只打印age=25和name=tom的信息
mysql> select * from cwh where age=10 and name='tom'; +----+------+------+ | id | name | age | +----+------+------+ | 1 | tom | 10 | +----+------+------+ 1 row in set (0.00 sec)
8.查看錶格打印id在2-4之間的信息
mysql> select * from cwh where id between 2 and 4; +----+---------+------+ | id | name | age | +----+---------+------+ | 2 | jerry | 20 | | 3 | natasha | 30 | | 4 | aaa | NULL | +----+---------+------+ 3 rows in set (0.00 sec)
9.查看錶格打印age爲空的信息
mysql> select * from cwh where age is null; +----+------+------+ | id | name | age | +----+------+------+ | 4 | aaa | NULL | | 5 | bbb | NULL | | 6 | ccc | NULL | +----+------+------+ 3 rows in set (0.00 sec)
10.查看錶格打印age不爲空的信息
mysql> select * from cwh where age is not null; +----+---------+------+ | id | name | age | +----+---------+------+ | 1 | tom | 10 | | 2 | jerry | 20 | | 3 | natasha | 30 | +----+---------+------+ 3 rows in set (0.00 sec)
4.2.3 update語句
//DML操做之改操做update
//語法：UPDATE table_name SET column1 = new_value1[,column2 = new_value2,...] [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];
注意：此語句只能一條一條的修改記錄，能夠修改一條記錄中的多個字段
1.修改表中的aaa的age由null改成40
mysql> update cwh set age=40 where name='aaa'; Query OK, 1 row affected (0.00 sec) mysql> select * from cwh; +----+---------+------+ | id | name | age | +----+---------+------+ | 1 | tom | 10 | | 2 | jerry | 20 | | 3 | natasha | 30 | | 4 | aaa | 40 | | 5 | bbb | NULL | | 6 | ccc | NULL | +----+---------+------+ 6 rows in set (0.00 sec)
2.修改表中一行記錄中多個字段將id=6的ccc改成cwh，age改成60
mysql> update cwh set name='cwh',age=60 where id=6; Query OK, 1 row affected (0.00 sec) Rows matched: 1 Changed: 1 Warnings: 0 mysql> select * from cwh; +----+---------+------+ | id | name | age | +----+---------+------+ | 1 | tom | 10 | | 2 | jerry | 20 | | 3 | natasha | 30 | | 4 | aaa | 40 | | 5 | bbb | NULL | | 6 | cwh | 60 | +----+---------+------+ 6 rows in set (0.00 sec)
4.2.4 delete語句
//DML操做之刪操做delete
//語法：DELETE FROM table_name [WHERE clause] [ORDER BY 'column_name' [DESC]] [LIMIT [m,]n];
1.刪除某條記錄
mysql> select * from cwh; +----+---------+------+ | id | name | age | +----+---------+------+ | 1 | tom | 10 | | 2 | jerry | 20 | | 3 | natasha | 30 | | 4 | aaa | 40 | | 5 | bbb | NULL | | 6 | cwh | 60 | +----+---------+------+ 6 rows in set (0.00 sec) mysql> delete from cwh where id=5; Query OK, 1 row affected (0.00 sec) mysql> select * from cwh; +----+---------+------+ | id | name | age | +----+---------+------+ | 1 | tom | 10 | | 2 | jerry | 20 | | 3 | natasha | 30 | | 4 | aaa | 40 | | 6 | cwh | 60 | +----+---------+------+ 5 rows in set (0.00 sec)
2.刪除整個表的內容
mysql> select * from cwh111; +----+------+------+ | id | name | age | +----+------+------+ | 1 | qqq | 10 | | 2 | www | 20 | +----+------+------+ 2 rows in set (0.00 sec) mysql> delete from cwh111; Query OK, 2 rows affected (0.00 sec) mysql> select * from cwh111; Empty set (0.00 sec)
4.2.5 truncate語句
truncate與delete的區別:
| 語句類型 | 特色 |
|---|---|
| delete | DELETE刪除表內容時僅刪除內容，但會保留表結構 DELETE語句每次刪除一行，並在事務日誌中爲所刪除的每行記錄一項 能夠經過回滾事務日誌恢復數據 很是佔用空間 |
| truncate | 刪除表中全部數據，且沒法恢復 表結構、約束和索引等保持不變，新添加的行計數值重置爲初始值 執行速度比DELETE快，且使用的系統和事務日誌資源少 經過釋放存儲表數據所用的數據頁來刪除數據，而且只在事務日誌中記錄頁的釋放 對於有外鍵約束引用的表，不能使用TRUNCATE TABLE刪除數據 不能用於加入了索引視圖的表 |
mysql> select * from cwh111; +----+------+------+ | id | name | age | +----+------+------+ | 1 | qqq | 10 | | 2 | www | 20 | +----+------+------+ 2 rows in set (0.00 sec) mysql> truncate cwh111; Query OK, 0 rows affected (0.01 sec) mysql> select * from cwh111; Empty set (0.00 sec)
4.3 DCL操做
4.3.1 建立受權grant
權限類型(priv_type)
| 權限類型 | 表明什麼? |
|---|---|
| ALL | 全部權限 |
| SELECT | 讀取內容的權限 |
| INSERT | 插入內容的權限 |
| UPDATE | 更新內容的權限 |
| DELETE | 刪除內容的權限 |
指定要操做的對象db_name.table_name
| 表示方式 | 意義 |
|---|---|
| *.* | 全部庫的全部表 |
| db_name | 指定庫的全部表 |
| db_name.table_name | 指定庫的指定表 |
WITH GRANT OPTION：被受權的用戶可將本身的權限副本轉贈給其餘用戶，說白點就是將本身的權限徹底複製給另外一個用戶。不建議使用。
語法：GRANT priv_type,... ON [object_type] db_name.table_name TO ‘username'@'host' [IDENTIFIED BY 'password'] [WITH GRANT OPTION];
1.受權cwh用戶在數據庫本機上登陸訪問全部數據庫
mysql> grant all on *.* to cwh@127.0.0.1 identified by '+7p6Mg2JsHgX1bIaOSwSykG8O2M='; //此處密碼使用openssl rand 20 -base64 生成
mysql> show grants for cwh@127.0.0.1
-> ;
+--------------------------------------------------+
| Grants for cwh@127.0.0.1 |
+--------------------------------------------------+
| GRANT ALL PRIVILEGES ON *.* TO 'cwh'@'127.0.0.1' |
+--------------------------------------------------+
1 row in set (0.00 sec)
2.受權cwh用戶在192.168.112.149上遠程登陸訪問chengweihong數據庫
//首先受權 mysql> grant all on chengweihong.* to cwh@192.168.112.149 identifiied by '+7p6Mg2JsHgX1bIaOSwSykG8O2M='; Query OK, 0 rows affected, 1 warning (0.00 sec) //在查看受權內容 mysql> show grants for cwh@192.168.112.149; +---------------------------------------------------------------------+ | Grants for cwh@192.168.112.149 | +---------------------------------------------------------------------+ | GRANT USAGE ON *.* TO 'cwh'@'192.168.112.149' | | GRANT ALL PRIVILEGES ON `chengweihong`.* TO 'cwh'@'192.168.112.149' | +---------------------------------------------------------------------+ 2 rows in set (0.00 sec) //最後在192.168.112.149主機上驗證 [root@146 ~]# mysql -ucwh -p -h192.168.112.146 Enter password: MySQL [(none)]> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | chengweihong | +--------------------+ 2 rows in set (0.00 sec) MySQL [chengweihong]> show tables; +------------------------+ | Tables_in_chengweihong | +------------------------+ | cwh | | cwh111 | +------------------------+ 2 rows in set (0.00 sec)
3.受權cwh用戶在全部位置上遠程登陸訪問chengweihong數據庫的cwh表
//首先受權 mysql> grant all on chengweihong.cwh to 'cwh'@'%' identified by '+7p6Mg2JsHgX1bIaOSwSykG8O2M='; Query OK, 0 rows affected, 1 warning (0.00 sec) //在查看權限 mysql> show grants for cwh@'%'; +-----------------------------------------------------------+ | Grants for cwh@% | +-----------------------------------------------------------+ | GRANT USAGE ON *.* TO 'cwh'@'%' | | GRANT ALL PRIVILEGES ON `chengweihong`.`cwh` TO 'cwh'@'%' | +-----------------------------------------------------------+ 2 rows in set (0.00 sec) //在146主機上驗證 [root@146 ~]# mysql -ucwh -p -h192.168.112.146 Enter password: Welcome to the MariaDB monitor. Commands end with ; or \g. Your MySQL connection id is 11 Server version: 5.7.25 MySQL Community Server (GPL) Copyright (c) 2000, 2018, Oracle, MariaDB Corporation Ab and others. Type 'help;' or '\h' for help. Type '\c' to clear the current input statement. MySQL [(none)]> show databases; +--------------------+ | Database | +--------------------+ | information_schema | | chengweihong | +--------------------+ 2 rows in set (0.00 sec) MySQL [(none)]> show tables from chengweihong; +------------------------+ | Tables_in_chengweihong | +------------------------+ | cwh | +------------------------+ 1 row in set (0.00 sec)
4.3.2 查看受權
1.查看當前登陸用戶的受權信息
mysql> show grants; +---------------------------------------------------------------------+ | Grants for root@localhost | +---------------------------------------------------------------------+ | GRANT ALL PRIVILEGES ON *.* TO 'root'@'localhost' WITH GRANT OPTION | | GRANT PROXY ON ''@'' TO 'root'@'localhost' WITH GRANT OPTION | +---------------------------------------------------------------------+ 2 rows in set (0.00 sec)
2.查看指定用戶cwh的受權信息
mysql> show grants for cwh@'%'; +-----------------------------------------------------------+ | Grants for cwh@% | +-----------------------------------------------------------+ | GRANT USAGE ON *.* TO 'cwh'@'%' | | GRANT ALL PRIVILEGES ON `chengweihong`.`cwh` TO 'cwh'@'%' | +-----------------------------------------------------------+ 2 rows in set (0.00 sec)
4.3.3 取消受權REVOKE
//語法：REVOKE priv_type,... ON db_name.table_name FROM 'username'@'host';
1.取消對cwh用戶的受權
mysql> revoke all on chengweihong.cwh from cwh@'%'; Query OK, 0 rows affected (0.00 sec) mysql> show grants for cwh@'%'; +---------------------------------+ | Grants for cwh@% | +---------------------------------+ | GRANT USAGE ON *.* TO 'cwh'@'%' | +---------------------------------+ 1 row in set (0.00 sec)
注意：mysql服務進程啓動時會讀取mysql庫中的全部受權表至內存中：
- GRANT或REVOKE等執行權限操做會保存於表中，mysql的服務進程會自動重讀受權表，並更新至內存中
- 對於不可以或不能及時重讀受權表的命令，可手動讓mysql的服務進程重讀受權表
刷新受權表：
mysql> FLUSH PRIVILEGES;
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