SQL Server：选择具有最新更新报告的组

Question

我需要一个选择查询来根据其中更新的最新报告列出ReportGroups。

例如，此查询列出报告组的最大创建日期：

SELECT TOP 100 PERCENT rg.ReportGroupID
FROM Report.ReportGroups as rg
INNER JOIN Report.Reports as r ON rg.ReportGroupID = r.ReportGroupID
GROUP BY rg.ReportGroupID
ORDER BY MAX(CreateDate) DESC

输出：

20|2015-02-28
8 |2015-02-17
1 |2015-02-10
36|2015-01-11
25|2014-12-20
18|2014-12-16

现在，我需要所有ReportGroup列：

SELECT * 
FROM Report.ReportGroups 
WHERE ReportGroupID IN (
    SELECT TOP 100 PERCENT rg.ReportGroupID
    FROM Report.ReportGroups as rg
    INNER JOIN Report.Reports as r ON rg.ReportGroupID = r.ReportGroupID
    GROUP BY rg.ReportGroupID
    ORDER BY MAX(CreateDate) DESC
)

输出：

1 |Group 1
8 |Group 8
18|Group 18
20|Group 20
25|Group 25
36|Group 36

但是此查询的结果不像上一个查询那样排序。

谢谢。

Answer 1

您可以使用外部应用来执行此操作：

SELECT
  rg.*
FROM 
  Report.ReportGroups as rg
  outer apply (
    select top 1 r.CreateDate 
    from Report.Reports as r
    where rg.ReportGroupID = r.ReportGroupID
    order by r.CreateDate DESC
  ) r
ORDER BY 
    r.CreateDate DESC

Answer 2

我认为这就是您要寻找的。 更改为基于联接的选择，并按内部（最大）createdate进行排序。

SELECT rg1.* 
FROM Report.ReportGroups rg1
JOIN (
    SELECT TOP 100 PERCENT rg.ReportGroupID, MAX(CreateDate) createdate
    FROM Report.ReportGroups as rg
    INNER JOIN Report.Reports as r ON rg.ReportGroupID = r.ReportGroupID
    GROUP BY rg.ReportGroupID
    ORDER BY MAX(CreateDate) DESC
) trg ON rg1.ReportGroupID = trg.ReportGroupID
ORDER BY trg.createdate;