Mysql查询不同的随机条件

Question

我需要从我的问题库中随机提问。我有一张表 QUESTION，列为:questionType。我需要根据用户的请求从我的表中随机获取问题。

例如，他选择，questionType:['Identification', 'Multiple Choice'] 以及每个 questionType 的问题数量:['10', '20']。

所以我需要从 questionType 列中随机查询 10 个值为 Identification 的问题，并从 questionType 列中查询另外 20 个随机问题，值为 Multiple Choice。

我有这个sql语句:

SELECT question FROM QUESTION WHERE questionType = 'Identification' ORDER BY RAND() LIMIT 10;

那么如何添加条件:

questionType = 'Multiple Choice' ORDER BY RAND() LIMIT 20

你能帮帮我吗？谢谢!

Answer 1

试试这个:

SELECT question FROM 
(
(SELECT question FROM QUESTION WHERE questionType = 'Identification' ORDER BY RAND() LIMIT 10)
UNION ALL
(SELECT question FROM QUESTION WHERE questionType = 'Multiple Choice' ORDER BY RAND() LIMIT 20)
) T
ORDER BY RAND()

参见 SQL Fiddle 中的演示.