MySQL中的RAND()函數使用詳解_Mysql

MySQL RAND()函數調用可以在0和1之間產生一個隨機數：

mysql> SELECT RAND( ), RAND( ), RAND( );+------------------+-----------------+------------------+| RAND( )   | RAND( )   | RAND( )   |+------------------+-----------------+------------------+| 0.45464584925645 | 0.1824410643265 | 0.54826780459682 |+------------------+-----------------+------------------+1 row in set (0.00 sec)

當調用一個整數參數時，RAND()使用該隨機數發生器種子值。每次在給定值種子產生，RAND()會產生一個可重複的一系列數字：

mysql> SELECT RAND(1), RAND( ), RAND( );+------------------+------------------+------------------+| RAND(1 )   | RAND( )   | RAND( )   |+------------------+------------------+------------------+| 0.18109050223705 | 0.75023211143001 | 0.20788908117254 |+------------------+------------------+------------------+1 row in set (0.00 sec)

可以使用ORDER BY RAND()，隨機組行或值如下：

要瞭解ORDER BY RAND()函數, 假設EMPLOYEE_TBL的表有以下記錄：

mysql> SELECT * FROM employee_tbl;+------+------+------------+--------------------+| id | name | work_date | daily_typing_pages |+------+------+------------+--------------------+| 1 | John | 2007-01-24 |    250 || 2 | Ram | 2007-05-27 |    220 || 3 | Jack | 2007-05-06 |    170 || 3 | Jack | 2007-04-06 |    100 || 4 | Jill | 2007-04-06 |    220 || 5 | Zara | 2007-06-06 |    300 || 5 | Zara | 2007-02-06 |    350 |+------+------+------------+--------------------+7 rows in set (0.00 sec)

現在使用以下目錄：

mysql> SELECT * FROM employee_tbl ORDER BY RAND();+------+------+------------+--------------------+| id | name | work_date | daily_typing_pages |+------+------+------------+--------------------+| 5 | Zara | 2007-06-06 |    300 || 3 | Jack | 2007-04-06 |    100 || 3 | Jack | 2007-05-06 |    170 || 2 | Ram | 2007-05-27 |    220 || 4 | Jill | 2007-04-06 |    220 || 5 | Zara | 2007-02-06 |    350 || 1 | John | 2007-01-24 |    250 |+------+------+------------+--------------------+7 rows in set (0.01 sec)mysql> SELECT * FROM employee_tbl ORDER BY RAND();+------+------+------------+--------------------+| id | name | work_date | daily_typing_pages |+------+------+------------+--------------------+| 5 | Zara | 2007-02-06 |    350 || 2 | Ram | 2007-05-27 |    220 || 3 | Jack | 2007-04-06 |    100 || 1 | John | 2007-01-24 |    250 || 4 | Jill | 2007-04-06 |    220 || 3 | Jack | 2007-05-06 |    170 || 5 | Zara | 2007-06-06 |    300 |+------+------+------------+--------------------+7 rows in set (0.00 sec)