mysql> select * from category order by rand();
mysql> select * from category order by rand() limit 5 ;
+-------------+-------------+---------------------+
| category_id | name | last_update |
+-------------+-------------+---------------------+
| 6 | Documentary | 2006-02-15 04:46:27 |
| 1 | Action | 2006-02-15 04:46:27 |
| 13 | New | 2006-02-15 04:46:27 |
| 2 | Animation | 2006-02-15 04:46:27 |
| 11 | Horror | 2006-02-15 04:46:27 |
+-------------+-------------+---------------------+
5 rows in set (0.00 sec)
mysql> select * from category order by rand() limit 5 ;
+-------------+-----------+---------------------+
| category_id | name | last_update |
+-------------+-----------+---------------------+
| 16 | Travel | 2006-02-15 04:46:27 |
| 15 | Sports | 2006-02-15 04:46:27 |
| 13 | New | 2006-02-15 04:46:27 |
| 2 | Animation | 2006-02-15 04:46:27 |
| 7 | Drama | 2006-02-15 04:46:27 |
+-------------+-----------+---------------------+
5 rows in set (0.00 sec)
mysql>
原文：http://wangqh.blog.51cto.com/5367393/1769093