From 758046c5bb123aee742ad7169a11c15a7c459767 Mon Sep 17 00:00:00 2001
From: zhh <zhenghong1991@126.com>
Date: Tue, 11 Dec 2018 17:05:37 +0800
Subject: [PATCH] Create mysql.md

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