mysql - 行未按 group by 正确排序

Question

SELECT userid,SUBSTRING_INDEX(SUBSTRING_INDEX(data, '\"!', -1), '!\"', 1)+0 AS num 
FROM table
WHERE type=2
ORDER BY num DESC LIMIT 5

这会获取 !x! 之间的数字在一个字符串中并尝试返回数字并按该数字对行进行排序。它工作正常。

但是，我不知道如何返回唯一用户 ID。

添加 ORDER BY userid 返回不按 num 排序的行:

SELECT userid,SUBSTRING_INDEX(SUBSTRING_INDEX(data, '\"!', -1), '!\"', 1)+0 AS num 
FROM table
WHERE type=2
GROUP BY userid
ORDER BY num DESC LIMIT 5

Distinct 也不起作用:

SELECT DISTINCT(userid),SUBSTRING_INDEX(SUBSTRING_INDEX(data, '\"!', -1), '!\"', 1)+0 AS num 
FROM table
WHERE type=2
ORDER BY num DESC LIMIT 5

我没有想法..

例子:

id    userid     data
1       56       !100!
2       22       !90!
3       56       !200!

结果应该是:

userid      num
56          200
22          90

Answer 1

SELECT userid,MAX(num) num FROM
(SELECT userid,SUBSTRING_INDEX(SUBSTRING_INDEX(data, '\"!', -1), '!\"', 1)+0 AS num  
FROM table 
WHERE type=2) A
GROUP BY userid;