怎样用命令查看Mysql数据库大小？

mysql> use information_schema;

mysql> select TABLE_SCHEMA,TABLE_NAME,DATA_LENGTH from tables;  #通过在information_schema数据库的tables表中的数据，可以查看每个数据库的各个表所占空间大小（DATA_LENGTH是以Byte为单位）

1、使用 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 TABLES;

3、查看指定数据库的大小

比如说数据库test

select concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data from TABLES where table_schema='test';

4、查看指定数据库的表的大小

比如说数据库test中的test_user表

select concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data from TABLES where table_schema='test' and table_name='test_user';

==

MySQL数据库中的information_schema库的tables表的结构：

mysql> desc tables;
+-----------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+---------------------+------+-----+---------+-------+
| TABLE_CATALOG | varchar(512) | NO | | | |
| TABLE_SCHEMA | varchar(64) | NO | | | |
| TABLE_NAME | varchar(64) | NO | | | |
| TABLE_TYPE | varchar(64) | NO | | | |
| ENGINE | varchar(64) | YES | | NULL | |
| VERSION | bigint(21) unsigned | YES | | NULL | |
| ROW_FORMAT | varchar(10) | YES | | NULL | |
| TABLE_ROWS | bigint(21) unsigned | YES | | NULL | |
| AVG_ROW_LENGTH | bigint(21) unsigned | YES | | NULL | |
| DATA_LENGTH | bigint(21) unsigned | YES | | NULL | |
| MAX_DATA_LENGTH | bigint(21) unsigned | YES | | NULL | |
| INDEX_LENGTH | bigint(21) unsigned | YES | | NULL | |
| DATA_FREE | bigint(21) unsigned | YES | | NULL | |
| AUTO_INCREMENT | bigint(21) unsigned | YES | | NULL | |
| CREATE_TIME | datetime | YES | | NULL | |
| UPDATE_TIME | datetime | YES | | NULL | |
| CHECK_TIME | datetime | YES | | NULL | |
| TABLE_COLLATION | varchar(32) | YES | | NULL | |
| CHECKSUM | bigint(21) unsigned | YES | | NULL | |
| CREATE_OPTIONS | varchar(255) | YES | | NULL | |
| TABLE_COMMENT | varchar(2048) | NO | | | |
+-----------------+---------------------+------+-----+---------+-------+
21 rows in set (0.00 sec)

其中：
TABLE_SCHEMA 是数据库名
TABLE_NAME 是数据库中的表名
DATA_LENGTH 表的大小
INDEX_LENGTH 索引大小

==

参考网址：

http://www.apoyl.com/?p=458

更多MySQL命令小结：

use information_schema;
select concat(round(sum(DATA_LENGTH/1024/1024), 2), 'MB') as data from TABLES;

select concat(round(sum(DATA_LENGTH/1024/1024), 2), 'MB') as data from TABLES where table_schema= 'apoyl' ;

select concat(round(sum(DATA_LENGTH/1024/1024), 2), 'MB') as data from TABLES where table_schema= 'apoyl' and table_name= 'apoyl_test' ;

show databases;
show tables;

show processlist;

show variables like "plugin%";

select @@basedir;
/*
system_user()   系统用户名
user()          用户名
current_user    当前用户名
session_user()  连接数据库的用户名
database()      数据库名
version()       MYSQL数据库版本
load_file()     MYSQL读取本地文件的函数
@@datadir       读取数据库路径
@@basedir       MYSQL 安装路径
@@version_compile_os    操作系统
*/
select Host,User,Password from mysql.user;
select * from mysql.func;

show variables like '%skip_networking%';
show variables like 'collation_%';
show variables like 'char_%';

use db_name;
status;         #查看某个数据库的编码

show create database db_name;   #查看某个数据库的编码
show [global] status;
show variables;
show engines;
show grants;    #查看权限分配情况
show columns from db_name.tb_name;  <=> desc db_name.tb_name
show create table db_name.tb_name;

mysql> show tables from information_schema;
mysql> show index from information_schema.USER_PRIVILEGES;
mysql> select * from information_schema.user_privileges;