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我在 MySQL 成员和订阅者中有 2 个表。我想做的是；我想查找至少有 1 个过期订阅且没有有效订阅的订阅者。

SELECT mem.id as id 

FROM members as mem 
INNER JOIN subscriptions as sub ON sub.member_id = mem.id 

WHERE 
sub.active = 0 AND 
NOT EXISTS ( SELECT 1 FROM subscriptions as sub2 WHERE sub2.member_id = mem.id AND sub2.active = 1 )

Group By mem.id

这个查询处理时间太长（考虑到2张表的记录量，这是正常的）。

我等了大约 2 分钟才看到结果，但由于它仍在尝试加载，我只是取消了它。我需要更快的结果。有没有其他方法可以做到这一点？

感谢您的时间和关心。

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3 回答 3

1

我猜不出你为什么要这样做你的 sql 但这可能有效

SELECT mem.id as id 
FROM members as mem 
INNER JOIN subscriptions as sub ON sub.member_id = mem.id 
WHERE sub.active = 0 
Group By mem.id

更新：我猜您可能会添加deactivted_date列或其他内容以指示到期

于 2012-04-10T11:01:33.137 回答
1

干得好。（确保你有正确的索引）。另请注意，我离开了原始联接，因为我假设您在某些时候需要的不仅仅是 member_id。但是如果你想要的只是 member_id，你可以一起删除 members 表。

/*
insert members (member_name) values ('tom')
insert members (member_name) values ('bob')
insert members (member_name) values ('jim')

declare @tom int
set @tom = (select member_id from members where member_name = 'tom')

insert subscriptions (member_id, is_active) values (@tom, 1)
insert subscriptions (member_id, is_active) values (@tom, 0)

declare @bob int
set @bob = (select member_id from members where member_name = 'bob')

insert subscriptions (member_id, is_active) values (@bob, 0)
insert subscriptions (member_id, is_active) values (@bob, 0)
*/

SELECT m.member_id
FROM members as m 
INNER JOIN subscriptions as s ON s.member_id = m.member_id 
LEFT JOIN subscriptions s2 on s2.member_id = m.member_id and s2.is_active = 1
WHERE 
s.is_active = 0 and
s2.subscription_id is null

Group By m.member_id

或者

SELECT s.member_id
FROM subscriptions as s
LEFT JOIN subscriptions s2 on s2.member_id = s.member_id and s2.is_active = 1
WHERE 
s.is_active = 0 and
s2.subscription_id is null

Group By s.member_id
于 2012-04-10T11:21:08.183 回答
0

DISTINCT 和 group by 应该执行相同的操作，但我发现使用 DISTINCT 查询更具可读性。

活动索引可能会加快查询速度。

SELECT DISTINCT mem.id as id
FROM members as mem, subscriptions as sub WHERE sub.member_id = mem.id AND 
sub.active = 0 AND NOT EXISTS (
   SELECT * FROM subscriptions as sub2
   WHERE sub2.member_id = mem.id AND sub2.active = 1
)
于 2012-04-10T13:22:56.670 回答