如何查詢mysql數(shù)據(jù)庫中哪些表的數(shù)據(jù)量最大？
數(shù)據(jù)庫中有幾十上百張表，那么哪些表的數(shù)據(jù)量比較大呢，總不能一個(gè)表一個(gè)表的去查詢吧，在mysql中也有類似于oracle的數(shù)據(jù)字典表，只不過mysql沒有oracle記錄的那么多和詳細(xì)，但也足夠我們查詢這些信息了。
在mysql的information_schema下有存儲數(shù)據(jù)庫基本信息的數(shù)據(jù)字典表，可以通過查詢tables表來獲得所需要的表相關(guān)信息。
mysql> show databases;
+--------------------+
| Database |
+--------------------+
| information_schema |
|mysql |
|report |
| report_result |
|test |
+--------------------+
5 rows in set (0.02 sec)
mysql> use information_schema;
Database changed
mysql> show tables;
+---------------------------------------+
|Tables_in_information_schema |
+---------------------------------------+
|CHARACTER_SETS |
|COLLATIONS |
| COLLATION_CHARACTER_SET_APPLICABILITY |
|COLUMNS |
|COLUMN_PRIVILEGES |
|KEY_COLUMN_USAGE |
|PROFILING |
|ROUTINES |
|SCHEMATA |
|SCHEMA_PRIVILEGES |
|STATISTICS |
|TABLES |
|TABLE_CONSTRAINTS |
|TABLE_PRIVILEGES |
|TRIGGERS |
|USER_PRIVILEGES |
|VIEWS |
+---------------------------------------+
17 rows in set (0.00 sec)
那么我們查看一下talbes表結(jié)構(gòu)信息，看看存儲的具體信息
mysql> desc tables;
+-----------------+--------------+------+-----+---------+-------+
| Field |Type | Null | Key | Default |Extra |
+-----------------+--------------+------+-----+---------+-------+
| TABLE_CATALOG | varchar(512) | YES | | NULL | |
| TABLE_SCHEMA | varchar(64) | NO | | | |
| TABLE_NAME | varchar(64) | NO | | | |
| TABLE_TYPE | varchar(64) | NO | | | |
| ENGINE |varchar(64) | YES | |NULL | |
| VERSION |bigint(21) | YES | |NULL | |
| ROW_FORMAT | varchar(10) | YES | | NULL | |
| TABLE_ROWS | bigint(21) | YES | | NULL | |
| AVG_ROW_LENGTH | bigint(21) | YES | | NULL | |
| DATA_LENGTH | bigint(21) | YES | | NULL | |
| MAX_DATA_LENGTH | bigint(21) | YES | | NULL | |
| INDEX_LENGTH | bigint(21) | YES | | NULL | |
| DATA_FREE | bigint(21) |YES | | NULL | |
| AUTO_INCREMENT | bigint(21) | YES | | NULL | |
| CREATE_TIME | datetime |YES | | NULL | |
| UPDATE_TIME | datetime |YES | | NULL | |
| CHECK_TIME | datetime |YES | | NULL | |
| TABLE_COLLATION | varchar(64) | YES | |NULL | |
| CHECKSUM | bigint(21) |YES | | NULL | |
| CREATE_OPTIONS | varchar(255) | YES | |NULL | |
| TABLE_COMMENT | varchar(80) | NO | | | |
+-----------------+--------------+------+-----+---------+-------+
21 rows in set (0.00 sec)
主要存儲了表的信息如表使用的引擎，表的類型等信息。我們可以通過查詢table_rows屬性獲得哪些表數(shù)據(jù)量比較大。
mysql> select table_name,table_rows from tables order by table_rows desc limi 10;
+---------------+------------+
| table_name |table_rows |
+---------------+------------+
| task6 | 1558845 |
| task | 1554399 |
| task5 | 1539009 |
| task3 | 1532169 |
| task1 | 1531143 |
| task2 | 1531143 |
| task4 | 1521225 |
| task7 | 980865 |
我們繼續(xù)深入思考，這些存儲的數(shù)據(jù)是否準(zhǔn)確，是否真實(shí)的反應(yīng)了表中數(shù)據(jù)量大小？
mysql> show create table tables \G;
*************************** 1. row***************************
Table: TABLES
Create Table: CREATE TEMPORARY TABLE`TABLES` (
`TABLE_CATALOG` varchar(512) default NULL,
`TABLE_SCHEMA` varchar(64) NOT NULL default '',
`TABLE_NAME` varchar(64) NOT NULL default '',
`TABLE_TYPE` varchar(64) NOT NULL default '',
&nb
關(guān)鍵詞：mysql
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