sql - 如何用SQL UNION指定订单结果？

Question

我正在尝试运行以下查询:

select * from (select * from customquestionbank where questionid=6 or secondquestionid=6 
union select * from customquestionbank where questionid=5 or secondquestionid=5 
union select * from customquestionbank where questionid=10 or secondquestionid=10 
union select * from customquestionbank where questionid=11 or secondquestionid=11) Tabled

作为该网站的新手，我还无法发布图像，但结果如下:

questionid -> 5,6 ,10,11

但是，我希望结果以与上面的 select 语句相同的顺序显示。换句话说，questionid=6 首先返回，然后是 5，依此类推。

Answer 1

你不需要所有的联合，只需像这样:

SELECT DISTINCT * 
FROM   customquestionbank 
WHERE  questionid IN ( 6, 5, 10, 11 ) 
        OR secondquestionid IN ( 6, 5, 10, 11 ) 
ORDER  BY CASE 
            WHEN 6 IN ( questionid, secondquestionid ) THEN 0 
            WHEN 5 IN ( questionid, secondquestionid ) THEN 1 
            WHEN 10 IN ( questionid, secondquestionid ) THEN 2 
            WHEN 11 IN ( questionid, secondquestionid ) THEN 3 
          END