Question

我需要重新构建以下查询，以便改善性能和时间

考虑我的表格是录音和用户

录音表

bid | Date

1   | 02/10/2016 14:15:23
1   | 02/10/2016 10.30.15
1   | 02/09/2016 16.10.45
2   | 02/15/2016 14:15:23
2   | 01/10/2016 10.30.15
2   | 01/09/2016 16.10.45

用户表

id   | Udate               | Name

1    | 02/10/2016 15:15:23 | Bill
2    | 02/15/2016 14:15:23 | Max

我的要求是加入2个表格和

select max(date) from Recordings table group by bid with max(date)>udate

select distinct bid from Recordings ,users 
where Recordings.bid =users.id group by bid having max(date)>udate

由于

Answer 1

我不确定这一点，你的目的不客观。

SELECT bid, date , udate, name FROM Recordings
JOIN users on users.id = Recordings.bid
WHERE max(Recordings.udate) > users.date
GROUP BY bid

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Answer 2

我认为你正在寻找这样的东西：

SELECT id, uDate, name
FROM users
INNER JOIN
(
    SELECT bId, MAX(Date) as uDate
    FROM Recordings 
    GROUP BY bId
) x ON id = bId

如何连接两个表并使用分组选择最大值

2 个答案: