以下是相关表格的片段:
用户
| USER_UID | FIRSTNAME | LASTNAME |
abc123 bob smith
def456 rob smithies
ghi789 john clark
EVENT
| 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)
我有以下查询返回具有投票数的事件和基于此的排名:
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,我也想要返回1或0。
如果符合以下条件,用户将无资格投票:
用户是活动的所有者。
用户已经投票支持该事件(在event_vote中找到了用户uid和事件uid)。
... AS投票之后的以下代码在用户已经投票时给出了正确答案,但如果他们拥有该事件则没有。
,(
SELECT COUNT(*)
FROM event_vote ev
WHERE ev.event_uid = e.guid
AND ev.user_uid = '{$user_uid}'
) AS ineligible
预期结果(查看所有活动时从用户2s的角度来看)
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).
答案 0 :(得分:1)
您可以将此查询与case when
表达式一起使用,给出1或null
。这被聚合为count(distinct ...)
,仅当聚合值中至少有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rextester.com上看到它。
请注意,当您使用此类变量时,必须强制执行 inner 查询中的顺序。如果你只在外部查询上执行它,那么实际上已经太晚了,因为已经评估了变量表达式。它可能经常工作,因为优化器可能会考虑外部order by
,但不能保证。
答案 1 :(得分:0)
您需要检查User_Event表中的voted事件是否存在User_UID。如果是,选民就是所有者。
之类的:( PSEUDO我不在编译器附近)
IF EXISTS (Begin
select User_Event_Id
from User_event
where User_UId = @user_uid
(@user_uid the user trying to vote)
and where Event_Id = @Event
(@Event = event of the id, the user is trying to vote for)
End)
Begin
if(--Check if user has voted for event (code you already wrote)
--User is eligible
else
--User not eligible
End
ELSE
--User not eligible
但是,最好只花时间合并这两个请求,而不会产生if语句。