Mysql中随机函数笔记

Posted 2020-07-26 JAVA菜菜鸟

1，测试表结构：
mysql> desc test_user;
+---------+-------------+------+-----+---------+----------------+
        | Field   | Type        | Null | Key | Default | Extra          |
        +---------+-------------+------+-----+---------+----------------+
        | id      | int(11)     | NO   | PRI | NULL    | auto_increment |
        | name    | varchar(50) | NO   |     | NULL    |                |
        | age     | int(11)     | YES  |     | NULL    |                |
        | address | varchar(50) | YES  |     | NULL    |                |

2，添加随机字段和索引：
mysql> alter table test_user add random double;
mysql> alter table test_user add index (random)

3，填充随机字段数据:
mysql> update test_user set random = rand();

4,随机返回一条数据：

mysql> select id ,name from test_user where random > rand() order by random limit 1;

+----+------+
| id | name |
+----+------+
| 9 | com |
+----+------+
1 row in set (0.00 sec)

mysql> select id ,name from test_user where random > rand() order by random limi
t 1;
+----+------+
| id | name |
+----+------+
| 7 | www |
+----+------+
1 row in set (0.00 sec)