MySQL語法大全_本身整理的學習筆記

select * from emp;  #註釋

#---------------------------
#----命令行鏈接MySql---------

#啓動mysql服務器
net start mysql

#關閉   
net stop mysql  
 
#進入
mysql -h 主機地址 -u 用戶名 －p 用戶密碼 

#退出
exit

#---------------------------
#----MySql用戶管理---------

#修改密碼:首先在DOS 下進入mysql安裝路徑的bin目錄下，而後鍵入如下命令:
mysqladmin -uroot -p123 password 456;

#增長用戶
#格式:grant 權限 on 數據庫.* to 用戶名@登陸主機 identified by '密碼'
/*
如，增長一個用戶user1密碼爲password1，讓其能夠在本機上登陸， 並對全部數據庫有查詢、插入、修改、刪除的權限。首先用以root用戶連入mysql，而後鍵入如下命令： 
grant select,insert,update,delete on *.* to user1@localhost Identified by "password1"; 
若是但願該用戶可以在任何機器上登錄mysql，則將localhost改成"%"。 
若是你不想user1有密碼，能夠再打一個命令將密碼去掉。 
grant select,insert,update,delete on mydb.* to user1@localhost identified by ""; 
*/

grant all privileges on wpj1105.* to sunxiao@localhost identified by '123';   #all privileges 全部權限

#----------------------------
#-----MySql數據庫操做基礎-----

#顯示數據庫
show databases;

#判斷是否存在數據庫wpj1105,有的話先刪除
drop database if exists wpj1105;

#建立數據庫
create database wpj1105;

#刪除數據庫
drop database wpj1105;

#使用該數據庫
use wpj1105;

#顯示數據庫中的表
show tables;

#先判斷表是否存在,存在先刪除
drop table if exists student;

#建立表
create table student(
id int auto_increment primary key,
name varchar(50),
sex varchar(20),
date varchar(50),
content varchar(100)
)default charset=utf8;

#刪除表
drop table student;

#查看錶的結構
describe student;  #能夠簡寫爲desc student;

#插入數據
insert into student values(null,'aa','男','1988-10-2','......');
insert into student values(null,'bb','女','1889-03-6','......');
insert into student values(null,'cc','男','1889-08-8','......');
insert into student values(null,'dd','女','1889-12-8','......');
insert into student values(null,'ee','女','1889-09-6','......');
insert into student values(null,'ff','null','1889-09-6','......');
#查詢表中的數據
select * from student;
select id,name from student;

#修改某一條數據
update student set sex='男' where id=4;

#刪除數據
delete from student where id=5;

# and 且
select * from student where date>'1988-1-2' and date<'1988-12-1';

# or 或
select * from student where date<'1988-11-2' or date>'1988-12-1';
   
#between
select * from student where date between '1988-1-2' and '1988-12-1';

#in 查詢制定集合內的數據
select * from student where id in (1,3,5);

#排序 asc 升序  desc 降序
select * from student order by id asc;

#分組查詢 #聚合函數 
select max(id),name,sex from student group by sex;

select min(date) from student;

select avg(id) as '求平均' from student;

select count(*) from student;   #統計表中總數

select count(sex) from student;   #統計表中性別總數  如有一條數據中sex爲空的話,就不予以統計~

select sum(id) from student;

#查詢第i條之後到第j條的數據(不包括第i條)
select * from student limit 2,5;  #顯示3-5條數據

#鞏固練習
create table c(
 id int primary key auto_increment,
 name varchar(10) not null,
 sex varchar(50) ,  #DEFAULT '男' ,
 age int unsigned, #不能爲負值(如爲負值 則默認爲0)
 sno int unique    #不可重複
);

drop table c;
desc c;

insert into c (id,name,sex,age,sno) values (null,'濤哥','男',68,1);
insert into c (id,name,sex,age,sno) values (null,'aa','男',68,2);
insert into c (id,name,sex,age,sno) values (null,'平平','男',35,3);
...

select * from c;

#修改數據 
update c set age=66 where id=2;
update c set name='花花',age=21,sex='女' where id=2
delete from c where age=21;

#經常使用查詢語句
select name,age ,id from c
select * from c where age>40 and age<60;  #and
select * from c where age<40 or age<60;  #or
select * from c where age between 40 and 60 #between
select * from c where age in (30,48,68,99);     #in 查詢指定集合內的數據
select * from c order by age desc;      #order by （asc升序 des降序）

#分組查詢
select name,max(age) from c group by sex;  #按性別分組查年齡最大值
#聚合函數
select min(age) from c;
select avg(age) as '平均年齡 ' from c;
select count(*) from c;  #統計表中數據總數
select sum(age) from c;

#修改表的名字
#格式:alter table tbl_name rename to new_name
alter table c rename to a;
 
#表結構修改
create table test
(
id int not null auto_increment primary key, #設定主鍵
name varchar(20) not null default 'NoName', #設定默認值
department_id int not null,
position_id int not null,
unique (department_id,position_id) #設定惟一值
);

#修改表的名字
#格式:alter table tbl_name rename to new_name
alter table test rename to test_rename;

#向表中增長一個字段(列)
#格式:alter table tablename add columnname type;/alter table tablename add(columnname type);
alter table test add  columnname varchar(20);

#修改表中某個字段的名字
alter table tablename change columnname newcolumnname type;  #修改一個表的字段名
alter table test change name uname varchar(50);

select * from test;

#表position 增長列test
alter table position add(test char(10));
#表position 修改列test
alter table position modify test char(20) not null;
#表position 修改列test 默認值
alter table position alter test set default 'system';
#表position 去掉test 默認值
alter table position alter test drop default;
#表position 去掉列test
alter table position drop column test;
#表depart_pos 刪除主鍵
alter table depart_pos drop primary key;
#表depart_pos 增長主鍵
alter table depart_pos add primary key PK_depart_pos
(department_id,position_id);

#用文本方式將數據裝入數據庫表中（例如D:/mysql.txt）
load data local infile "D:/mysql.txt" into table MYTABLE;

#導入.sql文件命令（例如D:/mysql.sql）source d:/mysql.sql;  #或者  /. d:/mysql.sql;