mysql rand()函数调用可以在0和1之间产生一个随机数：
mysql> select rand( ), rand( ), rand( );+------------------+-----------------+------------------+| rand( ) | rand( ) | rand( ) |+------------------+-----------------+------------------+| 0.45464584925645 | 0.1824410643265 | 0.54826780459682 |+------------------+-----------------+------------------+1 row in set (0.00 sec)
当调用一个整数参数时，rand()使用该随机数发生器种子值。每次在给定值种子生成，rand()会产生一个可重复的一系列数字：
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()，随机组行或值如下：
要了解order by rand()函数, 假设employee_tbl的表有以下记录：
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)
现在使用以下目录：
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)