系統(tǒng)信息函數(shù)用來查詢mysql數(shù)據(jù)庫的系統(tǒng)信息
VERSION()返回?cái)?shù)據(jù)庫版本號(hào)
復(fù)制代碼 代碼如下:m.survivalescaperooms.com
mysql> SELECT VERSION();
+-------------------------+
| VERSION() |
+-------------------------+
| 5.5.28-0ubuntu0.12.10.2 |
+-------------------------+
row in set (0.00 sec)
我這里用的是基于ubuntu發(fā)行版，Linux Mint
CONNECTION_ID()返回?cái)?shù)據(jù)庫的連接次數(shù)
復(fù)制代碼 代碼如下:m.survivalescaperooms.com
mysql> SELECT CONNECTION_ID();
+-----------------+
| CONNECTION_ID() |
+-----------------+
| 36 |
+-----------------+
row in set (0.00 sec)
其實(shí)每次連接到mysql的時(shí)候就會(huì)有顯示
DATABASE()、SCHEMA()返回當(dāng)前數(shù)據(jù)庫名
復(fù)制代碼 代碼如下:m.survivalescaperooms.com
mysql> SELECT DATABASE(), SCHEMA();
+------------+----------+
| DATABASE() | SCHEMA() |
+------------+----------+
| person | person |
+------------+----------+
row in set (0.00 sec)
USER()、SYSTEM_USER()、SESSION_USER()返回當(dāng)前用戶
復(fù)制代碼 代碼如下:m.survivalescaperooms.com
mysql> SELECT USER(), SYSTEM_USER(), SESSION_USER();
+----------------+----------------+----------------+
| USER() | SYSTEM_USER() | SESSION_USER() |
+----------------+----------------+----------------+
| root@localhost | root@localhost | root@localhost |
+----------------+----------------+----------------+
row in set (0.00 sec)
CURRENT_USER()、CURRENT_USER返回當(dāng)前用戶
復(fù)制代碼 代碼如下:m.survivalescaperooms.com
mysql> SELECT CURRENT_USER(), CURRENT_USER;
+----------------+----------------+
| CURRENT_USER() | CURRENT_USER |
+----------------+----------------+
| root@localhost | root@localhost |
+----------------+----------------+
row in set (0.00 sec)
上面的三個(gè)和這兩個(gè)功能是一樣的
CHARSET(str)返回字符串str的字符集
復(fù)制代碼 代碼如下:m.survivalescaperooms.com
mysql> SELECT CHARSET('張三');
+-------------------+
| CHARSET('張三') |
+-------------------+
| utf8 |
+-------------------+
row in set (0.00 sec)
COLLATION(str)返回字符串str的字符排列方式
復(fù)制代碼 代碼如下:m.survivalescaperooms.com
mysql> SELECT COLLATION('張三');
+---------------------+
| COLLATION('張三') |
+---------------------+
| utf8_general_ci |
+---------------------+
row in set (0.00 sec)
LAST_INSERT_ID()返回最后生成的AUTO_INCREMENT值
復(fù)制代碼 代碼如下:m.survivalescaperooms.com
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 |
+----+
rows in set (0.00 sec)
mysql> SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
| 3 |
+------------------+
row in set (0.00 sec)
上面的語句首先創(chuàng)建了一張表t1，其中有一個(gè)自增字段id然后分三次插入NULL，使其自增
確認(rèn)已經(jīng)存在數(shù)據(jù)之后，使用LAST_INSERT_ID()獲取最后自動(dòng)生成的值
