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

+---------+

| data    |

+---------+

| 26.17MB |

+---------+

1 row in set (0.01 sec)

mysql> select concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data  from TABLES where table_schema='jishi' and table_name='a_ya';

+--------+

| data   |

+--------+

| 0.02MB |

+--------+

1 row in set (0.00 sec)

mysql> SELECT CONCAT(ROUND(SUM(index_length)/(1024*1024), 2), ' MB') AS 'Total Index Size' FROM TABLES  WHERE table_schema = 'jishi'; 

+------------------+

| Total Index Size |

+------------------+

| 0.94 MB          |

+------------------+

1 row in set (0.01 sec)

mysql> SELECT CONCAT(ROUND(SUM(index_length)/(1024*1024), 2), ' MB') AS 'Total Index Size' FROM TABLES  WHERE table_schema = 'test' and table_name='a_yuser'; 

+------------------+

| Total Index Size |

+------------------+

| 21.84 MB         |

+------------------+

1 row in set (0.00 sec)

mysql> show create table test.a_yuser\G;

*************************** 1. row ***************************

       Table: a_yuser

Create Table: CREATE TABLE `a_yuser` (

  `email` varchar(60) NOT NULL DEFAULT '',

  `user_name` varchar(60) NOT NULL DEFAULT '',

  KEY `cc` (`email`(5)),

  KEY `ccb` (`user_name`(5)),

  KEY `ccbc` (`email`(5),`user_name`(5))

) ENGINE=MyISAM DEFAULT CHARSET=utf8

1 row in set (0.00 sec)

ERROR: 

No query specified

mysql> select count(*) from test.a_yuser;

+----------+

| count(*) |

+----------+

|  1073607 |

+----------+

1 row in set (0.00 sec)

mysql> 

查看一个库中的情况...

mysql>  SELECT CONCAT(table_schema,'.',table_name) AS 'Table Name', CONCAT(ROUND(table_rows/1000000,4),'M') AS 'Number of Rows', CONCAT(ROUND(data_length/(1024*1024*1024),4),'G') AS 'Data Size', CONCAT(ROUND(index_length/(1024*1024*1024),4),'G') AS 'Index Size', CONCAT(ROUND((data_length+index_length)/(1024*1024*1024),4),'G') AS'Total'FROM information_schema.TABLES WHERE table_schema LIKE 'test';

+---------------+----------------+-----------+------------+---------+

| Table Name    | Number of Rows | Data Size | Index Size | Total   |

+---------------+----------------+-----------+------------+---------+

| test.a_br     | 0.4625M        | 0.0259G   | 0.0171G    | 0.0431G |

| test.a_skuclr | 0.7099M        | 0.0660G   | 0.0259G    | 0.0919G |

| test.a_yuser  | 1.0736M        | 0.0497G   | 0.0213G    | 0.0710G |

| test.test     | 0.0000M        | 0.0000G   | 0.0000G    | 0.0000G |

+---------------+----------------+-----------+------------+---------+

4 rows in set (0.13 sec)

原文：http://blog.sina.com.cn/s/blog_4c197d420101fbl9.html