轉自：http://www.cnblogs.com/lukcyjane/p/3849354.html

通過MySQL的 information_schema 資料庫，可查詢資料庫中每個表佔用的空間、表記錄的行數；該庫中有一個 TABLES 表，這個表主要欄位分別是：

TABLE_SCHEMA : 資料庫名
TABLE_NAME：表名
ENGINE：所使用的儲存引擎
TABLES_ROWS：記錄數
DATA_LENGTH：資料大小
INDEX_LENGTH：索引大小

其他欄位請參考MySQL的手冊，檢視一個表佔用空間的大小，那就相當於是 資料大小 + 索引大小 。

mysql> use information_schema;
Database changed
mysql> select concat(round(sum(DATA_LENGTH/1024/1024),2),'MB') as data  from TABLES;
+----------+
| data     |
+----------+
| 104.21MB |
+----------+
1 row in set (0.11 sec)

檢視指定庫的大小

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)

檢視指定庫的索引大小

mysql> SELECT CONCAT(ROUND(SUM(index_length)/(1024*1024), 2), ' MB') AS 'Total Index Size' FROM TABLES  WHERE table_schema = 'jishi'; 
+------------------+
| Total Index Size |
+------------------+
| 0.94 MB          |
+------------------+
1 row in set (0.01 sec)

檢視指定庫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 = '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)

檢視一個庫中的情況

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)

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