这是有问题的表的片段:
用户
| USER_UID | FIRSTNAME | LASTNAME |
abc123 bob smith
def456 rob smithies
ghi789 john clark
事件
| GUID | NAME |
ev1 event1
ev2 event2
ev3 event3
USER_EVENT
| USER_EVENT_ID | USER_UID | EVENT_UID |
1 abc123 ev1
2 def456 ev2
3 ghi789 ev3
EVENT_VOTE
| EVENT_VOTE_ID | USER_UID | EVENT_UID |
1 def456 ev1 (user2 voted for user1's event)
我有以下查询,它返回带有投票数和基于此的排名的事件:
SELECT t.*, @curRank := @curRank + 1 AS rank
FROM ( SELECT e.guid,
e.name,
( SELECT COUNT(ev.event_vote_id)
FROM event_vote ev
WHERE ev.event_uid = e.guid
) AS votes
FROM event e
) AS t
CROSS JOIN (SELECT @curRank := 0) r
ORDER BY votes DESC
如果用户没有资格投票,我还想返回 1 或 0。
在以下情况下,用户没有资格投票:
用户是事件的所有者。
用户已经为该事件投票(用户 uid 和事件 uid 可在 event_vote 中找到)。
如果用户已经投票,则...AS 投票后的以下代码给了我正确的响应,但如果他们拥有该事件,则不会。
,(
SELECT COUNT(*)
FROM event_vote ev
WHERE ev.event_uid = e.guid
AND ev.user_uid = '{$user_uid}'
) AS ineligible
预期结果(从用户 2 秒的角度查看所有事件)
guid: ev1
name: event1
votes: 1
rank: 1
ineligible: 1 (already voted).
guid: ev2
name: event2
votes: 0
rank: 2
ineligible: 1 (user owns this event)
guid: ev3
name: event3
votes: 0
rank: 3
ineligible: 0 (user doesn't own this event and has yet to vote).
您可以将此查询与case when
给出 1 或null
. 这被聚合为 a count(distinct ...)
,仅当聚合值中至少有一个 1 时才给出 1,否则为 0:
SELECT t.*,
@curRank := @curRank + 1 AS rank
FROM (
SELECT u.user_uid,
e.guid,
e.name,
count(ev.user_uid) votes,
count(distinct
case when u.user_uid in (ev.user_uid, ue.user_uid)
then 1
end) ineligible
FROM user u
CROSS JOIN event e
INNER JOIN user_event ue
ON ue.event_uid = e.guid
LEFT JOIN event_vote ev
ON ev.event_uid = e.guid
GROUP BY u.user_uid,
e.guid
ORDER BY votes desc,
e.guid,
u.user_uid
) as t
CROSS JOIN (SELECT @curRank := 0) r
WHERE t.user_uid = 'def456'
ORDER BY votes desc,
guid,
user_uid
在reextester.com上查看它的运行情况。
请注意,当您使用这样的变量时,您必须强制内部查询中的顺序。如果您只在外部查询上执行此操作,那么它真的来得太晚了,因为变量表达式已经被评估了。虽然它可能经常工作,因为优化器可能会考虑到外部order by
,但不能保证。
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