MySQL培訓教程：MySQL系統信息函數有哪些
最新學訊：近期OCP認證正在報名中，因考試人員較多請盡快報名獲取最近考試時間，報名費用請聯系在線老師，甲骨文官方認證，報名從速！
我要咨詢mysql系統信息函數有哪些？VERSION()返回數據庫版本號，CONNECTION_ID()返回數據庫的連接次數，DATABASE()、SCHEMA()返回當前數據庫名，USER()、SYSTEM_USER()、SESSION_USER()返回當前用戶，CURRENT_USER()、CURRENT_USER返回當前用戶，CHARSET(str)返回字符串str的字符集，COLLATION(str)返回字符串str的字符排列方式，LAST_INSERT_ID()返回最后生成的AUTO_INCREMENT值
VERSION()返回數據庫版本號
mysql> SELECT VERSION(); +-------------------------+ | VERSION() | +-------------------------+ | 5.5.28-0ubuntu0.12.10.2 | +-------------------------+ 1 row in set (0.00 sec)
我這里用的是基于ubuntu發行版，Linux Mint
CONNECTION_ID()返回數據庫的連接次數
mysql> SELECT CONNECTION_ID(); +-----------------+ | CONNECTION_ID() | +-----------------+ | 36 | +-----------------+ 1 row in set (0.00 sec)
其實每次連接到mysql的時候就會有顯示
DATABASE()、SCHEMA()返回當前數據庫名
mysql> SELECT DATABASE(), SCHEMA(); +------------+----------+ | DATABASE() | SCHEMA() | +------------+----------+ | person | person | +------------+----------+ 1 row in set (0.00 sec)
USER()、SYSTEM_USER()、SESSION_USER()返回當前用戶
mysql> SELECT USER(), SYSTEM_USER(), SESSION_USER(); +----------------+----------------+----------------+ | USER() | SYSTEM_USER() | SESSION_USER() | +----------------+----------------+----------------+ | root@localhost | root@localhost | root@localhost | +----------------+----------------+----------------+ 1 row in set (0.00 sec)
CURRENT_USER()、CURRENT_USER返回當前用戶
mysql> SELECT CURRENT_USER(), CURRENT_USER; +----------------+----------------+ | CURRENT_USER() | CURRENT_USER | +----------------+----------------+ | root@localhost | root@localhost | +----------------+----------------+ 1 row in set (0.00 sec)
上面的三個和這兩個功能是一樣的
CHARSET(str)返回字符串str的字符集
mysql> SELECT CHARSET('張三'); +-------------------+ | CHARSET('張三') | +-------------------+ | utf8 | +-------------------+ 1 row in set (0.00 sec)
COLLATION(str)返回字符串str的字符排列方式
mysql> SELECT COLLATION('張三'); +---------------------+ | COLLATION('張三') | +---------------------+ | utf8_general_ci | +---------------------+ 1 row in set (0.00 sec)
LAST_INSERT_ID()返回最后生成的AUTO_INCREMENT值
mysql> CREATE TABLE t1(id INT PRIMARY KEY AUTO_INCREMENT); Query OK, 0 rows affected (0.10 sec) mysql> INSERT INTO t1 VALUES(NULL); Query OK, 1 row affected (0.04 sec) mysql> INSERT INTO t1 VALUES(NULL); Query OK, 1 row affected (0.03 sec) mysql> INSERT INTO t1 VALUES(NULL); Query OK, 1 row affected (0.04 sec) mysql> SELECT * FROM t1; +----+ | id | +----+ | 1 | | 2 | | 3 | +----+ 3 rows in set (0.00 sec) mysql> SELECT LAST_INSERT_ID(); +------------------+ | LAST_INSERT_ID() | +------------------+ | 3 | +------------------+ 1 row in set (0.00 sec)
上面的語句首先創建了一張表t1，其中有一個自增字段id
然后分三次插入NULL，使其自增
確認已經存在數據之后，使用LAST_INSERT_ID()獲取最后自動生成的值
