一对多连接中的限制记录

Question

我正在尝试生成记录列表，其中标头包含单个记录，并且日志中的FIRST条目表示记录的创建日期。 所有其他详细记录都是不必要的，并且在我只需要第一个时会创建多个结果。

我已经尝试过“分组依据”，自我加入，独立等，但是到目前为止，我所做的一切都没有达到预期的效果。 我觉得我在这里确实缺少一些明显的东西。

这就是我正在使用的：

SELECT i.id
    ,l.CreateDate
    ,i.departmentname
    ,i.productkey
    ,c.Description
FROM dbo.table i (NOLOCK)

JOIN dbo.log l ON i.id = l.id

JOIN dbo.LU_Table c ON i.id = c.ID

WHERE l.CreateDate > '2019-04-01'

AND l.CreateDate < '2019-04-30'

我想看看：

ID# 1, 04/05/2019, Department, Product, Description
ID# 2, 04/05/2019, Department, Product, Description
ID# 3, 04/05/2019, Department, Product, Description
ID# 4, 04/05/2019, Department, Product, Description

相反，我得到：

ID# 1, 04/05/2019, Department, Product, Description
ID# 1, 04/06/2019, Department, Product, Description
ID# 1, 04/07/2019, Department, Product, Description
ID# 1, 04/08/2019, Department, Product, Description
ID# 1, 04/09/2019, Department, Product, Description
ID# 2, 04/05/2019, Department, Product, Description
ID# 2, 04/06/2019, Department, Product, Description
ID# 2, 04/07/2019, Department, Product, Description
ID# 2, 04/08/2019, Department, Product, Description
ID# 2, 04/09/2019, Department, Product, Description

Answer 1

我认为最简单的方法是将Order By放在where子句之后。 因此它看起来像是ORDER BY l.CreateDate, i.id ASC ，应该可以解决问题。

Answer 2

您似乎想要：

SELECT i.id, l.CreateDate, i.departmentname, i.productkey, c.Description
FROM dbo.table i JOIN
     (SELECT l.id, MIN(l.CreateDate) as CreateDate
      FROM dbo.log l
      GROUP BY l.id
     ) l
     ON i.id = l.id JOIN
     dbo.LU_Table c
     ON i.id = c.ID
WHERE l.CreateDate > '2019-04-01' AND
      l.CreateDate < '2019-04-30';

Answer 3

我从查询中了解到的是，有一个表名表我有一个ID记录，而日志表可能有多个记录针对每个ID。

您可以通过为日志表创建派生表来实现。

衍生表

Select  row_number() over(partition by ID order by ID) srno     
          , ID 
          , creation_date
   From log

尝试这个

SELECT i.id
    ,l.CreateDate
    ,i.departmentname
    ,i.productkey
    ,c.Description
FROM dbo.table i (NOLOCK)
JOIN (Select  row_number() over(partition by ID order by ID) srno       
              , ID 
              , creation_date
       From log ) l  on l.id = i.id and  l.srno = 1

JOIN dbo.LU_Table c ON i.id = c.ID
WHERE l.CreateDate > '2019-04-01'

AND l.CreateDate < '2019-04-30'