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.user\G
*************************** 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)