面试官：MySQL怎么查看表占用空间大小

前言

在mysql中有一个默认的数据表information_schema，information_schema这张数据表保存了MySQL服务器所有数据库的信息。如数据库名，数据库的表，表栏的数据类型与访问权限等。

再简单点，这台MySQL服务器上，到底有哪些数据库、各个数据库有哪些表，每张表的字段类型是什么，各个数据库要什么权限才能访问，等等信息都保存在information_schema表里面，所以请勿删改此表。整理了一份328页MySQLPDF文档

代码

1，切换数据库

use information_schema;

2，查看数据库使用大小

select concat(round(sum(data_length/1024/1024),2),’MB’) as data from tables where table_schema=’DB_Name’ ;

3，查看表使用大小

select concat(round(sum(data_length/1024/1024),2),’MB’) as data from tables where table_schema=’DB_Name’ and table_name=’Table_Name’;

网上找的一个，亲测可用:

• 先进去MySQL自带管理库：information_schema

• 然后查询 data_length,index_length

• 你自己的数据库名：dbname

• 你自己的表名：tablename

    mysql> use information_schema;
    Database changed
    mysql> select data_length,index_length
    -> from tables where
    -> table_schema='dbname'
    -> and table_name = 'tablename';
    +-------------+--------------+
    | data_length | index_length |
    +-------------+--------------+
    | 166379520 | 235782144 |
    +-------------+--------------+
    row in set (0.02 sec)

    mysql> select concat(round(sum(data_length/1024/1024),2),'MB') as data_length_MB,
    -> concat(round(sum(index_length/1024/1024),2),'MB') as index_length_MB
    -> from tables where
    -> table_schema='dbname'
    -> and table_name = 'tablename';
    +----------------+-----------------+
    | data_length_MB | index_length_MB |
    +----------------+-----------------+
    | 158.67MB | 224.86MB |
    +----------------+-----------------+
    row in set (0.03 sec)

1.查看所有数据库容量大小

select
table_schema as '数据库',
sum(table_rows) as '记录数',
sum(truncate(data_length/1024/1024, 2)) as '数据容量(MB)',
sum(truncate(index_length/1024/1024, 2)) as '索引容量(MB)'
from information_schema.tables
group by table_schema
order by sum(data_length) desc, sum(index_length) desc;

2.查看所有数据库各表容量大小

select
table_schema as '数据库',
table_name as '表名',
table_rows as '记录数',
truncate(data_length/1024/1024, 2) as '数据容量(MB)',
truncate(index_length/1024/1024, 2) as '索引容量(MB)'
from information_schema.tables
order by data_length desc, index_length desc;

3.查看指定数据库容量大小

例：查看mysql库容量大小

select
table_schema as '数据库',
sum(table_rows) as '记录数',
sum(truncate(data_length/1024/1024, 2)) as '数据容量(MB)',
sum(truncate(index_length/1024/1024, 2)) as '索引容量(MB)'
from information_schema.tables
where table_schema='mysql';

4.查看指定数据库各表容量大小

例：查看mysql库各表容量大小

select
table_schema as '数据库',
table_name as '表名',
table_rows as '记录数',
truncate(data_length/1024/1024, 2) as '数据容量(MB)',
truncate(index_length/1024/1024, 2) as '索引容量(MB)'
from information_schema.tables
where table_schema='mysql'
order by data_length desc, index_length desc;

select concat(round(sum(data_length/1024/1024),2),'MB') as data_length_MB, concat(round(sum(index_length/1024/1024),2),'MB') as index_length_MB
from tables 
where table_schema='passport' and table_name='tb_user_info';

-- 569.98MB 141.98MB

select concat(round(sum(data_length/1024/1024),2),'MB') as data_length_MB, concat(round(sum(index_length/1024/1024),2),'MB') as index_length_MB
from tables
where table_schema='passport_v2' and table_name='tb_user_info';

-- 2128.94MB 285.00MB 整理了一份328页MySQLPDF文档