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+# Mysql常用命令
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+
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+## 数据定义语句(DDL)
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+
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+### 数据库操作
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+
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+- 登录数据库:mysql -uroot -proot
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+- 创建数据库:create database test
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+- 查看所有数据库:show databases
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+- 使用数据库:use test
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+- 查看所有数据表:show tables
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+- 删除数据库:drop database test
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+
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+### 表操作
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+
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+- 创建表:create table emp(ename varchar(10),hiredate date,sal decimal(10,2),deptno int(2))
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+ create table dept(deptno int(2),deptname varchar(10))
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+- 查看表的定义:desc emp
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+- 查看表定义(详细):show create table emp \G
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+- 删除表:drop table emp
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+- 修改表字段:alter table emp modify ename varchar(20)
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+- 添加表字段:alter table emp add column age int(3)
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+- 删除表字段:alter table emp drop column age
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+- 字段改名;alter table emp change age age1 int(4)
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+- 修改表名:alter table emp rename emp1
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+
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+## 数据操纵语句(DML)
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+
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+### 插入记录
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+
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+- 指定名称插入:insert into emp (ename,hiredate,sal,deptno) values ('zhangsan','2018-01-01','2000',1)
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+- 不指定名称插入:insert into emp values ('lisi','2018-01-01','2000',1)
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+- 批量插入数据:insert into dept values(1,'dept1'),(2,'dept2')
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+
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+### 修改记录
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+
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+update emp set sal='4000',deptno=2 where ename='zhangsan'
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+
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+### 删除记录
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+
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+delete from emp where ename='zhangsan'
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+
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+### 查询记录
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+
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+- 查询所有记录:select * from emp
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+- 查询不重复的记录:select distinct deptno from emp
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+- 条件查询:select * from emp where deptno=1 and sal<3000
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+- 排序和限制:select * from emp order by deptno desc limit 2
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+- 聚合(查询部门人数大于1的部门编号):select deptno,count(1) from emp group by deptno having count(1) > 1
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+- 连接查询:select * from emp e left join dept d on e.deptno=d.deptno
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+- 子查询:select * from emp where deptno in (select deptno from dept)
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+- 记录联合:select deptno from emp union select deptno from dept
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+
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+## 数据控制语句(DCL)
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+
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+- 授予操作权限:grant select,insert on test.* to 'test'@'localhost' identified by '123'
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+- 收回操作权限:revoke insert on test.* from 'test'@'localhost'
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+
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+## 其他
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+
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+### 字符集相关
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+- 查看字符集:show variables like 'character%'
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+- 创建数据库时指定字符集:create database test1 character set utf8
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