《MYSQL數(shù)據(jù)庫(kù)MySQL筆記之系統(tǒng)信息函數(shù)詳解》要點(diǎn)：
本文介紹了MYSQL數(shù)據(jù)庫(kù)MySQL筆記之系統(tǒng)信息函數(shù)詳解，希望對(duì)您有用。如果有疑問，可以聯(lián)系我們。
系統(tǒng)信息函數(shù)用來查詢mysql數(shù)據(jù)庫(kù)的系統(tǒng)信息
VERSION()返回?cái)?shù)據(jù)庫(kù)版本號(hào)
MYSQL實(shí)例
代碼如下:
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(kù)的連接次數(shù)
MYSQL實(shí)例
代碼如下:
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(kù)名
MYSQL實(shí)例
代碼如下:
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
MYSQL實(shí)例
代碼如下:
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
代碼如下:
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
MYSQL實(shí)例
代碼如下:
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
代碼如下:
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
代碼如下:
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實(shí)例
mysql> INSERT INTO t1 VALUES(NULL);
Query OK, 1 row affected (0.03 sec)MYSQL實(shí)例
mysql> INSERT INTO t1 VALUES(NULL);
Query OK, 1 row affected (0.04 sec)MYSQL實(shí)例
mysql> SELECT * FROM t1;
+----+
| id |
+----+
|? 1 |
|? 2 |
|? 3 |
+----+
?rows in set (0.00 sec)MYSQL實(shí)例
mysql> SELECT LAST_INSERT_ID();
+------------------+
| LAST_INSERT_ID() |
+------------------+
|??????????????? 3 |
+------------------+
?row in set (0.00 sec)
MYSQL實(shí)例
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MYSQL實(shí)例
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MYSQL實(shí)例
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