在MySQL数据库中，有一个内置的database叫做information_schema, 该数据库中的tables表包含了数据库中所有表的基本信息,tables表结构如下：
mysql> use information_schema;
Database changed
mysql> describe tables;
+-----------------+---------------------+------+-----+---------+-------+
| Field | Type | Null | Key | Default | Extra |
+-----------------+---------------------+------+-----+---------+-------+
| TABLE_CATALOG | varchar(512) | NO | | | |
| TABLE_SCHEMA | varchar(64) | NO | | | |
| TABLE_NAME | varchar(64) | NO | | | |
| TABLE_TYPE | varchar(64) | NO | | | |
| ENGINE | varchar(64) | YES | | NULL | |
| VERSION | bigint(21) unsigned | YES | | NULL | |
| ROW_FORMAT | varchar(10) | YES | | NULL | |
| TABLE_ROWS | bigint(21) unsigned | YES | | NULL | |
| AVG_ROW_LENGTH | bigint(21) unsigned | YES | | NULL | |
| DATA_LENGTH | bigint(21) unsigned | YES | | NULL | |
| MAX_DATA_LENGTH | bigint(21) unsigned | YES | | NULL | |
| INDEX_LENGTH | bigint(21) unsigned | YES | | NULL | |
| DATA_FREE | bigint(21) unsigned | YES | | NULL | |
| AUTO_INCREMENT | bigint(21) unsigned | YES | | NULL | |
| CREATE_TIME | datetime | YES | | NULL | |
| UPDATE_TIME | datetime | YES | | NULL | |
| CHECK_TIME | datetime | YES | | NULL | |
| TABLE_COLLATION | varchar(32) | YES | | NULL | |
| CHECKSUM | bigint(21) unsigned | YES | | NULL | |
| CREATE_OPTIONS | varchar(255) | YES | | NULL | |
| TABLE_COMMENT | varchar(2048) | NO | | | |
+-----------------+---------------------+------+-----+---------+-------+
21 rows in set (0.03 sec)
下面介绍几个主要关键字段：
- TABLE_SCHEMA: 表所属的数据库名
- TABLE_NAME: 表名
- TABLE_ROWS: 表行数
- DATA_LENGTH: 数据总大小
- INDEX_LENGTH: 索引总大小
- DATA_FREE: 磁盘碎片大小
查看表大小语句示例如下：
mysql> select table_schema, table_name, concat(truncate(sum(DATA_LENGTH)/1024/1024,2),' MB') as data_size,concat(truncate(sum(DATA_FREE)/1024/1024,2),' MB') as data_free,concat(truncate(sum(INDEX_LENGTH)/1024/1024,2),'MB') as index_size from information_schema.tables where TABLE_SCHEMA='test' and table_name='alert_message_box';
+--------------+---------------------+-------------+-----------+------------+
| table_schema | table_name | data_size | data_free | index_size |
+--------------+---------------------+-------------+-----------+------------+
| test | alert_message_box | 16462.00 MB | 0.00 MB | 23287.00MB |
+--------------+---------------------+-------------+-----------+------------+
1 row in set (0.00 sec)
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最后编辑时间为: Apr 17, 2018 at 01:07 pm