SQL语句（方便记忆版）

1.  DML

2. DDL

3.  例子

-- 建表

use mydb;

createtable user(

userid int,

username varchar(20),

password varchar(20)

);

-- 添加字段到首列 first

-- alter table user add email VARCHAR(20)  first;

-- 修改字段 change

alter table user change email email varchar(50) after userid;

-- 删除字段  drop

alter table user drop phone;

-- 批量插入数据

-- insert intouser(username,password,email)values('ls','123','ls@qq.com'),('ls','123','ls@qq.com');

-- 将user表中的数据整体插入到user2中

insert intousers select * from user

-- 更新操作

update tbname set 字段=新值 [where ]

update user set username = 'ww' where userid =3;

-- 删除操作

delete from tbname [where]

delete from user where userid = 4;