MySQL管理一些基础SQL语句

1、进入information_schema 数据库（存放了其他的数据库的信息）
use information_schema;

2、查询所有数据的大小：
select concat(round(sum(data_length/1024/1024),2),'MB') as data from information_schema.tables;

3、查看指定数据库的大小：
比如查看数据库home的大小
select concat(round(sum(data_length/1024/1024),2),'MB') as data from tables where table_schema='home';

查看数据所占的空间大小 
SELECT CONCAT(ROUND(SUM(data_length)/(1024*1024),2) + ROUND(SUM(index_length)/(1024*1024),2),'MB') AS 'DB Size'
  FROM information_schema.`TABLES` WHERE table_schema='dbname'


4、查看指定数据库的某个表的大小
比如查看数据库home中 members 表的大小
select concat(round(sum(data_length/1024/1024),2),'MB') as data from tables where table_schema='home' and table_name='members';
select concat(round(sum(data_length/1024/1024),2),'MB') as data from information_schema.tables where table_schema='dbname' and table_name='t_msg_app_new';

5、查看指定数据库的表的大小 大到小
SELECT table_name,CONCAT(ROUND((data_length/1024/1024),2),'MB') AS DATA FROM TABLES WHERE table_schema='dbname'  ORDER BY data_length DESC;

6、查看指定数据库表的创建时间，更新时间。
SELECT table_name,create_time,update_time FROM information_schema.`TABLES`  WHERE  table_schema='dbname'  ORDER BY update_time DESC

SELECT table_name,table_rows,create_time,update_time
FROM information_schema.`TABLES`  WHERE  table_schema='dbname'  and table_name='tablename' ORDER BY update_time DESC


7、查看所有存储引擎为MyISAM的表
SELECT * FROM `information_schema`.`TABLES` WHERE TABLE_SCHEMA='dbname' AND `engine`='MyISAM'

8、查询表中的所有列
SELECT GROUP_CONCAT(column_name)AS namestr
FROM information_schema.`COLUMNS`  WHERE  table_name='tablename' ;

9、查询表中的所有列(拼接插入INSERT SQL)
SELECT CONCAT('INSERT INTO ',table_name,'(',GROUP_CONCAT(column_name),')VALUES()')AS namestr
FROM information_schema.`COLUMNS`  WHERE   table_schema='dbname' AND table_name='tablename' ;

10、#查看是否开启事件
select @@event_scheduler