通过MySQL的information_schema数据库，可查询数据库中每个表占用的空间、表记录的行数；
该库中有一个TABLES表，这个表主要字段分别是：
TABLE_SCHEMA：数据库名
TABLE_NAME：表名
ENGINE：所使用的存储引擎
TABLES_ROWS：记录数
DATA_LENGTH：数据大小
INDEX_LENGTH：索引大小
其他字段请参考MySQL的手册，查看一个表占用空间的大小，那就相当于是数据大小 + 索引大小 。
查看所有库的大小
mysql> use information_schema;
Reading table information for completion of table and column names
You can turn off this feature to get a quicker startup with -A
Database changed
mysql> select concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data from TABLES;
+------------+
| data |
+------------+
| 550.82MB |
+------------+
1 row in set (0.17 sec)
查看指定库的大小
mysql> select concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data from TABLES where table_schema='mysql';
+---------+
| data |
+---------+
| 0.70MB |
+---------+
1 row in set (0.00 sec)
查看指定库的指定表的大小
mysql> select concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data from TABLES where table_schema='mysql' and table_name='user';
+---------+
| data |
+---------+
| 0.00MB |
+---------+
1 row in set (0.00 sec)
查看指定库的索引大小
mysql> SELECT CONCAT(ROUND(SUM(index_length)/(1024*1024), 2), ' MB') AS 'Total Index Size' FROM TABLES WHERE table_schema = 'mysql';
+------------------+
| Total Index Size |
+------------------+
| 0.10 MB |
+------------------+
1 row in set (0.00 sec)
查看指定库的指定表的索引大小
mysql> SELECT CONCAT(ROUND(SUM(index_length)/(1024*1024), 2), ' MB') AS 'Total Index Size' FROM TABLES WHERE table_schema = 'mysql' and table_name='user';
+------------------+
| Total Index Size |
+------------------+
| 0.00 MB |
+------------------+
1 row in set (0.00 sec)
mysql> show create table mysql.userG
*************************** 1. row ***************************
Table: user
Create Table: CREATE TABLE `user` (
`Host` char(60) COLLATE utf8_bin NOT NULL DEFAULT '',
`User` char(16) COLLATE utf8_bin NOT NULL DEFAULT '',
`Password` char(41) CHARACTER SET latin1 COLLATE latin1_bin NOT NULL DEFAULT '',
`Select_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Insert_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Update_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Delete_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Create_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Drop_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Reload_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Shutdown_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Process_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`File_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Grant_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`References_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Index_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Alter_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Show_db_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Super_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Create_tmp_table_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Lock_tables_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Execute_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Repl_slave_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Repl_client_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Create_view_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Show_view_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Create_routine_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Alter_routine_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Create_user_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Event_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Trigger_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`Create_tablespace_priv` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
`ssl_type` enum('','ANY','X509','SPECIFIED') CHARACTER SET utf8 NOT NULL DEFAULT '',
`ssl_cipher` blob NOT NULL,
`x509_issuer` blob NOT NULL,
`x509_subject` blob NOT NULL,
`max_questions` int(11) unsigned NOT NULL DEFAULT '0',
`max_updates` int(11) unsigned NOT NULL DEFAULT '0',
`max_connections` int(11) unsigned NOT NULL DEFAULT '0',
`max_user_connections` int(11) unsigned NOT NULL DEFAULT '0',
`plugin` char(64) COLLATE utf8_bin DEFAULT 'mysql_native_password',
`authentication_string` text COLLATE utf8_bin,
`password_expired` enum('N','Y') CHARACTER SET utf8 NOT NULL DEFAULT 'N',
PRIMARY KEY (`Host`,`User`)
) ENGINE=MyISAM DEFAULT CHARSET=utf8 COLLATE=utf8_bin COMMENT='Users and global privileges'
1 row in set (0.00 sec)
mysql> select count(*) from mysql.user;
+----------+
| count(*) |
+----------+
| 20 |
+----------+
1 row in set (0.00 sec)
查询指定数据库中每个表的总行数,数据大小,索引大小和总大小
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 'mysql';
+---------------------------------+----------------+-----------+------------+---------+
| Table Name | Number of Rows | Data Size | Index Size | Total |
+---------------------------------+----------------+-----------+------------+---------+
| mysql.columns_priv | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.db | 0.0001M | 0.0000G | 0.0000G | 0.0000G |
| mysql.event | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.func | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.general_log | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.help_category | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.help_keyword | 0.0006M | 0.0001G | 0.0000G | 0.0001G |
| mysql.help_relation | 0.0012M | 0.0000G | 0.0000G | 0.0000G |
| mysql.help_topic | 0.0006M | 0.0005G | 0.0000G | 0.0006G |
| mysql.ndb_binlog_index | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.plugin | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.proc | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.procs_priv | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.proxies_priv | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.servers | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.slow_log | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.tables_priv | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.time_zone | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.time_zone_leap_second | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.time_zone_name | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.time_zone_transition | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.time_zone_transition_type | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
| mysql.user | 0.0000M | 0.0000G | 0.0000G | 0.0000G |
+---------------------------------+----------------+-----------+------------+---------+
23 rows in set (0.00 sec)
查询数据库指定表的数据部分大小,索引部分大小和总占用磁盘大小
mysql> SELECT
a.table_schema ,
a.table_name ,
concat(round(sum(DATA_LENGTH / 1024 / 1024) + sum(INDEX_LENGTH / 1024 / 1024) ,2) ,'MB') total_size ,
concat(round(sum(DATA_LENGTH / 1024 / 1024) , 2) ,'MB') AS data_size ,
concat(round(sum(INDEX_LENGTH / 1024 / 1024) , 2) ,'MB') AS index_size
FROM
information_schema. TABLES a
WHERE
a.table_schema = '数据库'
AND a.table_name = '表名';
+----------------+-------------+-----------+-----------+------------+
| table_schema | table_name | total_size | data_size | index_size|
+---------------+--------------+-----------+-----------+------------+
| mysql | user | 0.00MB | 0.00MB | 0.00MB |
+---------------+---------------+-----------+-----------+-----------+
1 row in set (0.00 sec)