Question

我有2个表，我拿着记录如下

查询为

Select   BMC.JCRS_Mem_crs_Code,
         BMC.JCRS_Mem_Description,
         BMC.JCRS_Mem_Date,
         BJCM.JCRS_Mast_Title
From     Bus_MemberCourse BMC
Inner Join Bus_JourneymanCourseMaster BJCM
    On BMC.JCRS_Mem_crs_Code = BJCM.JCRS_Mast_Code
Where    BMC.JCRS_Mem_Completed = 1
         And BMC.JCRS_Mem_mem_ID = 5010
Group By BMC.JCRS_Mem_crs_Code,
         BMC.JCRS_Mem_Description,
         BMC.JCRS_Mem_Date,
         BJCM.JCRS_Mast_Title

但我想要的是我需要在Jcrs_mem_crs_code和Jcrs_mem_description上进行分组，如果这2列数据是常见的，那么我只想从这多个日期获取最新日期。即我只想选择该行并忽略其他行。

Answer 1

您只想要MAX(date)：

Select   BMC.JCRS_Mem_crs_Code,
         BMC.JCRS_Mem_Description,
         MAX(BMC.JCRS_Mem_Date) as JCRS_Mem_Date,
         BJCM.JCRS_Mast_Title
From     Bus_MemberCourse BMC
Inner Join Bus_JourneymanCourseMaster BJCM
    On BMC.JCRS_Mem_crs_Code = BJCM.JCRS_Mast_Code
Where BMC.JCRS_Mem_Completed = 1
And   BMC.JCRS_Mem_mem_ID = 5010
Group By BMC.JCRS_Mem_crs_Code,
         BMC.JCRS_Mem_Description,
         BJCM.JCRS_Mast_Title

Answer 2

您根本不需要Group by（您的查询中没有进行任何聚合）。

这可以通过Row_Number()窗口函数轻松完成，这两个列上的Partition按日期排序：

;With Cte As
(
    Select   BMC.JCRS_Mem_crs_Code,
             BMC.JCRS_Mem_Description,
             BMC.JCRS_Mem_Date,
             BJCM.JCRS_Mast_Title,
             Row_Number() Over (Partition By BMC.JCRS_Mem_crs_Code,
                                             BMC.JCRS_Mem_Description
                                Order By     BMC.JCRS_Mem_Date Desc) As RN
    From     Bus_MemberCourse BMC
    Inner Join Bus_JourneymanCourseMaster BJCM
        On BMC.JCRS_Mem_crs_Code = BJCM.JCRS_Mast_Code
    Where    BMC.JCRS_Mem_Completed = 1
             And BMC.JCRS_Mem_mem_ID = 5010
)
Select  JCRS_Mem_crs_Code,
        JCRS_Mem_Description,
        JCRS_Mem_Date,
        JCRS_Mast_Title
From    Cte
Where   RN = 1

获取最新的2列和日期组

2 个答案: