我有一个数据库,人们可以在其中为不同地方的人提交选票。在给定的时间,我想找出每个地方谁的票数最多。 (一个人可以在两个不同的地方被投票)
这是我到目前为止的 SQL:
SELECT placeId, userVotedId, cnt
FROM
(SELECT uvo.userVotedId, p.placeId, count(*) as cnt
FROM users as u, users_votes as uvo, places as p
WHERE u.userId = uvo.userVotedId
AND p.placeId = uvo.placeId
GROUP BY userVotedId, placeId)
AS RESULT
这给了我这个结果:
现在,这些是我真正想要的行:
我的查询中缺少什么以便我可以得到它?
我希望每个地点都有一个结果。所以我应该只看到不同的 placeId,以及获得最多选票的 userVotedId。
如果出现平局,将随机抽取一名获胜者!
最佳答案
看来你还需要一个骨料。在您的 cnt
值和 GROUP BY placeId, userVotedId
上使用 MAX()
聚合:
SELECT placeId, userVotedId, max(cnt)
FROM
(
SELECT uvo.userVotedId, p.placeId, count(*) as cnt
FROM users as u
INNER JOIN users_votes as uvo
ON u.userId = uvo.userVotedId
INNER JOIN places as p
ON p.placeId = uvo.placeId
GROUP BY userVotedId, placeId
) AS RESULT
GROUP BY placeId, userVotedId
注意:我将您的查询更改为使用 JOIN
语法而不是表之间的逗号。
编辑,根据您的评论,以下内容应该有效:
select total.uservotedid,
total.placeid,
total.cnt
from
(
SELECT uvo.userVotedId, p.placeId, count(*) as cnt
FROM users as u
INNER JOIN users_votes as uvo
ON u.userId = uvo.userVotedId
INNER JOIN places as p
ON p.placeId = uvo.placeId
GROUP BY userVotedId, placeId
) total
inner join
(
select max(cnt) Mx, placeid
from
(
SELECT uvo.userVotedId, p.placeId, count(*) as cnt
FROM users as u
INNER JOIN users_votes as uvo
ON u.userId = uvo.userVotedId
INNER JOIN places as p
ON p.placeId = uvo.placeId
GROUP BY userVotedId, placeId
) mx
group by placeid
) src
on total.placeid = src.placeid
and total.cnt = src.mx
结果是:
| USERVOTEDID | PLACEID | CNT |
-------------------------------
| 65 | 11 | 1 |
| 67 | 13 | 1 |
| 67 | 25 | 1 |
| 67 | 51 | 2 |
编辑#2,如果你想在平局时返回一个随机数,那么你可以使用用户变量:
select uservotedid,
placeid,
cnt
from
(
select total.uservotedid,
total.placeid,
total.cnt,
@rownum := case when @prev = total.placeid then @rownum+1 else 1 end rownum,
@prev := total.placeid pplaceid
from
(
SELECT uvo.userVotedId, p.placeId, count(*) as cnt
FROM users as u
INNER JOIN users_votes as uvo
ON u.userId = uvo.userVotedId
INNER JOIN places as p
ON p.placeId = uvo.placeId
GROUP BY userVotedId, placeId
) total
inner join
(
select max(cnt) Mx, placeid
from
(
SELECT uvo.userVotedId, p.placeId, count(*) as cnt
FROM users as u
INNER JOIN users_votes as uvo
ON u.userId = uvo.userVotedId
INNER JOIN places as p
ON p.placeId = uvo.placeId
GROUP BY userVotedId, placeId
) mx
group by placeid
) src
on total.placeid = src.placeid
and total.cnt = src.mx
order by total.placeid, total.uservotedid
) src
where rownum = 1
order by placeid, uservotedid
关于mysql - 如何获得每组的最大行数?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/14513383/