MySQL 提供幾種辦法以使獲取關於數據庫和數據庫裏各種對象(也就是數據庫的元數據)的信息,如下:
- SHOW語句,如SHOW TABLES等等。
- INFORMATION_SCHEMA數據庫裏的數據表。
- 命令行程序,如mysqlshow或者是mysqldump。
mysql> show tables from information_schema;
+---------------------------------------+
| Tables_in_information_schema |
+---------------------------------------+
| CHARACTER_SETS |
| COLLATIONS |
| COLLATION_CHARACTER_SET_APPLICABILITY |
| COLUMNS |
| COLUMN_PRIVILEGES |
| ENGINES |
| EVENTS |
| FILES |
| GLOBAL_STATUS |
| GLOBAL_VARIABLES |
| KEY_COLUMN_USAGE |
| PARTITIONS |
| PLUGINS |
| PROCESSLIST |
| PROFILING |
| REFERENTIAL_CONSTRAINTS |
| ROUTINES |
| SCHEMATA |
| SCHEMA_PRIVILEGES |
| SESSION_STATUS |
| SESSION_VARIABLES |
| STATISTICS |
| TABLES |
| TABLE_CONSTRAINTS |
| TABLE_PRIVILEGES |
| TRIGGERS |
| USER_PRIVILEGES |
| VIEWS |
+---------------------------------------+
28 rows in set (0.01 sec)
分別對這些列簡單的說明。- SCHEMATA、TABLES、VIEWS、ROUTIMES、TRIGGERS、EVENTS、PARTITIONS、COLUMNS,表示的信息分別是數據庫,數據表,視圖,存儲例程,觸發器,數據庫裏的事件,數據表分區和數據列的信息,以數據表爲例,就是TABLES表,有以下列:
這是我查看一些數據表的記錄mysql> show columns from INFORMATION_SCHEMA.COLUMNS; +--------------------------+---------------------+------+-----+---------+-------+ | Field | Type | Null | Key | Default | Extra | +--------------------------+---------------------+------+-----+---------+-------+ | TABLE_CATALOG | varchar(512) | YES | | NULL | | | TABLE_SCHEMA | varchar(64) | NO | | | | | TABLE_NAME | varchar(64) | NO | | | | | COLUMN_NAME | varchar(64) | NO | | | | | ORDINAL_POSITION | bigint(21) unsigned | NO | | 0 | | | COLUMN_DEFAULT | longtext | YES | | NULL | | | IS_NULLABLE | varchar(3) | NO | | | | | DATA_TYPE | varchar(64) | NO | | | | | CHARACTER_MAXIMUM_LENGTH | bigint(21) unsigned | YES | | NULL | | | CHARACTER_OCTET_LENGTH | bigint(21) unsigned | YES | | NULL | | | NUMERIC_PRECISION | bigint(21) unsigned | YES | | NULL | | | NUMERIC_SCALE | bigint(21) unsigned | YES | | NULL | | | CHARACTER_SET_NAME | varchar(32) | YES | | NULL | | | COLLATION_NAME | varchar(32) | YES | | NULL | | | COLUMN_TYPE | longtext | NO | | NULL | | | COLUMN_KEY | varchar(3) | NO | | | | | EXTRA | varchar(27) | NO | | | | | PRIVILEGES | varchar(80) | NO | | | | | COLUMN_COMMENT | varchar(255) | NO | | | | +--------------------------+---------------------+------+-----+---------+-------|
mysql> SELECT * FROM INFORMATION_SCHEMA.TABLES WHERE TABLE_SCHEMA != 'information_schema' and TABLE_SCHEMA!='mysql'\G; *************************** 1. row *************************** TABLE_CATALOG: NULL TABLE_SCHEMA: db_info TABLE_NAME: i_node TABLE_TYPE: BASE TABLE ENGINE: MyISAM VERSION: 10 ROW_FORMAT: Dynamic TABLE_ROWS: 11 AVG_ROW_LENGTH: 21 DATA_LENGTH: 240 MAX_DATA_LENGTH: 281474976710655 INDEX_LENGTH: 2048 DATA_FREE: 0 AUTO_INCREMENT: 16 CREATE_TIME: 2012-09-07 03:07:37 UPDATE_TIME: 2012-09-23 07:57:37 CHECK_TIME: NULL TABLE_COLLATION: latin1_swedish_ci CHECKSUM: NULL CREATE_OPTIONS: TABLE_COMMENT: *************************** 2. row *************************** TABLE_CATALOG: NULL TABLE_SCHEMA: db_info TABLE_NAME: test TABLE_TYPE: BASE TABLE ENGINE: MyISAM VERSION: 10 ROW_FORMAT: Fixed TABLE_ROWS: 3 AVG_ROW_LENGTH: 7 DATA_LENGTH: 21 MAX_DATA_LENGTH: 1970324836974591 INDEX_LENGTH: 1024 DATA_FREE: 0 AUTO_INCREMENT: NULL CREATE_TIME: 2012-09-22 02:25:01 UPDATE_TIME: 2012-09-22 02:37:18 CHECK_TIME: NULL TABLE_COLLATION: latin1_swedish_ci CHECKSUM: NULL CREATE_OPTIONS: TABLE_COMMENT: *************************** 3. row *************************** TABLE_CATALOG: NULL TABLE_SCHEMA: test TABLE_NAME: test TABLE_TYPE: BASE TABLE ENGINE: MyISAM VERSION: 10 ROW_FORMAT: Dynamic TABLE_ROWS: 3 AVG_ROW_LENGTH: 20 DATA_LENGTH: 60 MAX_DATA_LENGTH: 281474976710655 INDEX_LENGTH: 1024 DATA_FREE: 0 AUTO_INCREMENT: NULL CREATE_TIME: 2012-09-07 20:44:41 UPDATE_TIME: 2012-09-07 20:44:41 CHECK_TIME: NULL TABLE_COLLATION: latin1_swedish_ci CHECKSUM: NULL CREATE_OPTIONS: TABLE_COMMENT: 3 rows in set (0.00 sec)
- FILES。關於NDB硬盤數據文件的信息。
- TABLE_CONSTRAINS、KEY_COLUMN_USAGE:關於數據表和數據列上的約束條件的信息,一般唯一化索引和外鍵都屬於這些約束條件。
- STATISTICS。關於數據表索引特性的信息。
- REFERENTIAL_CONSTRAINS。關於外鍵的信息。
- CHARACTER_SETS、COLLATIONS、COLLATION_CHARACTER_SET_APPLICABILITY。關於所支持的字符集,每種字符集的排序方式、每種排序方式與它的字符集的映射關係信息。
- ENGINES、PLUGINS。關於存儲引擎和服務器插件的信息。
- USER_PRIVILEGES、SCHEMA_PRIVILEGES、TABLE_PRIVILEGES、COLUMN_PRIVILEGES。全局、數據庫、數據表和數據列的權限信息。這些信息分別來自mysql數據庫裏的user,db,tables_priv,column_priv數據表。
- PROCESSLIST。在服務器內執行的線程的信息。
- GLOBAL_VARIABLES、SESSION_VARIABLES、GLOBAL_STATUS、SESSION_STATUS。全局和會話級系統變量和狀態變量的值。
mysqlshow[選項] [db_name [tbl_name [col_name]]]
- 如果沒有給出數據庫,顯示所有匹配的數據庫。
- 如果沒有給出表,顯示數據庫中所有匹配的表。
- 如果沒有給出列,顯示錶中所有匹配的列和列類型。
- --keys . 查看某給定數據表裏的索引信息。
- --status 。 查看某給定數據庫裏的數據表的描述性信息。如:
[root@localhost ~]# mysqlshow --status db_info Database: db_info +--------+--------+---------+------------+------+----------------+-------------+------------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------+ | Name | Engine | Version | Row_format | Rows | Avg_row_length | Data_length | Max_data_length | Index_length | Data_free | Auto_increment | Create_time | Update_time | Check_time | Collation | Checksum | Create_options | Comment | +--------+--------+---------+------------+------+----------------+-------------+------------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------+ | i_node | MyISAM | 10 | Dynamic | 11 | 21 | 240 | 281474976710655 | 2048 | 0 | 16 | 2012-09-07 03:07:37 | 2012-09-23 07:57:37 | | latin1_swedish_ci | | | | | test | MyISAM | 10 | Fixed | 3 | 7 | 21 | 1970324836974591 | 1024 | 0 | | 2012-09-22 02:25:01 | 2012-09-22 02:37:18 | | latin1_swedish_ci | | | | +--------+--------+---------+------------+------+----------------+-------------+------------------+--------------+-----------+----------------+---------------------+---------------------+------------+-------------------+----------+----------------+---------