连接表的最后一条记录

我正在查找正确的SQL代码来连接两个表并仅显示详细信息表的最后一条记录。连接表的最后一条记录

我有2个表的数据块，

Deals 
    DealID 
    Dealname 
    DealDetails 

DealComments 
    dcID 
    DealID 
    CommentTime 
    CommentPerson 
    Comment

有每笔交易多份意见，但我想创建一个显示所有优惠只在最后一评论的来自每一笔交易视图（由CommentTime）字段确定

来源

2009-07-03 Khalid Rahaman

你想要什么，如果对于一些交易有两个或更多最后的评论与完全相同的时间？ – 2009-07-04 23:22:58

select a.dealid 
, a.dealname 
, a.dealdetails 
, b.dcid 
, b.commenttime 
, b.commentperson 
, b.comment 
from deals a, dealcomments b 
where b.dealid = a.dealid 
    and b.commenttime = (select max(x.commenttime) 
         from dealcomments x 
         where x.dealid = b.dealid)

编辑：我没看过最初的问题足够接近，并没有注意到，都需要在查看所有优惠券行。下面是我的修订答案：

select a.dealid 
, a.dealname 
, a.dealdetails 
, b.dcid 
, b.commenttime 
, b.commentperson 
, b.comment 
from deals a left outer join (select x.dcid 
, x.dealid 
, x.commenttime 
, x.commentperson 
, x.comment 
from dealcomments x 
where x.commenttime = (select max(x1.commenttime) 
         from dealcomments x1 
         where x1.dealid = x.dealid)) b 
on (a.dealid = b.dealid)

来源

2009-07-03 08:04:14

这个效果很好，但它只返回有评论的交易。我还想看到没有评论的交易 – 2009-07-04 20:27:27

@Khalid - 我编辑了我的答案，新的SQL应返回所有交易行。 – 2009-07-04 23:08:33

优秀，正是我所需要的。感谢John – 2009-07-05 05:24:17

试试这个..

SELECT D.*,DC1.Comment 
FROM Deals AS D 
    INNER JOIN DealComments AS DC1 
     ON D.DealId = DC1.DealID 
    INNER JOIN 
    (
     SELECT 
      DealID, 
      MAX(CommentTime) AS CommentTime 
     FROM DealComments AS DC2 
     GROUP BY DealID 
    ) AS DC2 
     ON DC2.DealId = DC.DealId 
      AND DC2.CommentTime = DC1.CommentTime

来源

2009-07-03 08:12:09 Atul

不是很优雅，但在甲骨文的工作原理：

select dealid, 
     dealname, 
     dealdetails, 
     comment, 
from 
(
    select a.dealid, 
     a.dealname, 
     a.dealdetails, 
     b.commenttime, 
     b.comment, 
     max(commenttime) over (partition by a.dealid) as maxCommentTime 
    from deals a inner join dealcomments b on b.dealid = a.dealid 
) 
where comment = maxCommentTime

来源

2009-07-03 08:14:29

为什么你将其描述为“不太优雅”？ – 2009-11-03 15:15:47

试试这个：

CREATE VIEW DealsWithLastComment 
AS 
    SELECT 
     D.*, DC.* 
    FROM 
     Deals D INNER JOIN DealComments DC 
     ON D.DealID = DC.DealID 
     GROUP BY D.DealID, DC.CommentTime 
     HAVING DC.CommentTime = MAX(DC.CommentTime)

来源

2009-07-03 08:18:47 PatrikAkerstrand

select 
    d.DealID, dc1.dcID, dc1.Comment, dc1.CommentPerson, dc1.CommentTime 
from 
    Deals d 
inner join 
    DealComments dc1 on dc1.DealID = d.DealID 
where 
    dc1.CommentTime = (select max(dc2.CommentTime) from DealsComments dc2 where dc2.DealId = dc1.DealId)

来源

2009-07-03 08:20:15 bang

强制性无子查询无处回答：

select d.* 
     , dc.* 
from Deals d 
     left outer join DealComments dc 
     on d.DealID = dc.DealID 
     left outer join DealComments dc1 
     on d.DealID = dc1.DealID 
    and 
     dc1.CommentTime > dc.CommentTime 
where dc1.CommentTime is null

告诉我一切都在Deals和DealComments当存在比任何给定的时间注释为特定DealID大不CommentTime。

编辑：Alex Kuznetsov在评论中敏锐地指出：OP要求显示所有的交易 - 交易是否有评论与否。所以我把第一个JOIN从INNER更改为LEFT OUTER。

来源

2009-07-03 09:12:34 bernie

这个查询怎么样。

select * from Deals 
left join DealComments on Deals.DealID = DealComments.DealID and DealComments.CommentTime = (SELECT CommentTime FROM DealComments WHERE DealComments.DealID = Deals.DealID ORDER BY CommentTime DESC limit 1)

来源

2011-05-04 12:44:57

连接表的最后一条记录

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