1，查看所有数据库大小

use information_schema;

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

2，查看指定数据库大小

use information_schema;

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

3，查看指定数据库中指定表的大小

use information_schema;

select concat(round(sum(data_length/1024/1024),2),'MB') as data from tables where table_schema='dbname' and table_name='tbname';