Join表的最后记录

Question

我正在寻找正确的SQL代码来连接2个表并只显示详细信息表的最后一条记录.

我有一张带2张桌子的数据库,

Deals 
   DealID
   Dealname
   DealDetails

DealComments
   dcID
   DealID
   CommentTime
   CommentPerson
   Comment

每笔交易都有多条评论,但我想创建一个显示所有交易的VIEW,并且只显示每笔交易的最后一条评论(由CommentTime确定)字段

Answer 1

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:我没有仔细阅读初始问题,并没有注意到视图中需要所有DEALS行.以下是我修改的答案:

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)