MySQL基础

CentOS7安装MySQL

yum install mysql mysql-server mysql-devel
yum install mariadb
systemctl start mariadb

MySQL基础语句

db及用户操作

1. 创建用户：create user 'username' @ 'localhost' identified by 'password'
2. 赋予权限：grant select,update,insert,delete on dbname.tablename(*) to 'user'@'%'
3. 创建db并指定字符集：
   create database dbname default character set utf8mb4 collate utf8mb4_general_ci
4. 显示数据库字符集：show variables like "char%";
5. 某一行临时指定字符集： set names utf8mb4;

查询

1. 查看表结构：desc tb_name;
2. 查询所有：select * from tb_name;
3. 条件查询：select * from tb_name where a=b;
4. 查询时间段：select * from tb_name where date between '2016-08-01' and '2016-09-01'（左闭右开）
5. 返回数量：

select count(*) from ...
select count(*) from tb_name where job in ('CLERK', 'ANALYST');
select count(*) from tb_name where job is/is not NULL;
select count(*) from tb_name where (a>500 or b="xx") and c like 'J%';

6. 排序：select count(*) from tb_name order by xx, xxx desc
7. 复杂查询（联合）：
   select a.*, p.* from tb_1 as a left join tb_2 as p on a.id = p.user_id order by a.id desc limit 50;