MySql常用命令

-- 创建相同表命令

create table test like stu;

-- 给表增加列

alart table stu add qq varchar(20) NOT NULL COMMENT 'q';

-- 删除表列

alter table stu drop qq;

-- 创建视图和使用视图查询
create view student1990 as select stuId,name from student where year(birthday)=1990;

select * from student1990;

-- 通过information_schema查看数据库所有表
select * from information_schema.tables;

-- 数据库大小统计
select table_schema,SUM((AVG_ROW_LENGTH*TABLE_ROWS+INDEX_LENGTH))/1024
from information_schema.`TABLES`
where table_schema='hello'