使用SQL公用表表达式或任何其他方法的百分比好吗？

Question

获取数据集2我正在使用以下CTE

;WITH RecordsWithNoDuplicates_CTE (RowNo,[Name]
       ,[DateAdded]
      ,Reason
   ) AS
(
SELECT ROW_NUMBER() OVER (PARTITION BY name Order by DateAdded DESC) AS 'RowNo'
    ,Name,
    DateAdded,
    Reason
 FROM 
    MyTable
)
SELECT * FROM RecordsWithNoDuplicates_CTE where rowno=1

为获取数据集3，我正在执行以下操作

  ;WITH RecordsWithSpecificCase_CTE (RowNo,[Name]
           ,[DateAdded]
          ,Reason
       ) AS
    (
    SELECT ROW_NUMBER() OVER (PARTITION BY name Order by DateAdded DESC) AS 'RowNo'
        ,Name,
        DateAdded,
        Reason
     FROM 
        MyTable
    WHERE REASON='Case1'
    )
    SELECT * FROM RecordsWithSpecificCase_CTE where rowno=1

我需要计算特定于Datset2中所有记录的Reason = Case1的记录百分比

Answer 1

只是为了扩展上面的评论......

在您的情况下，我可能会首先制作视图或功能以获取最新记录。这个 只是CTE周围的包装，并且会阻止你复制它。

CREATE VIEW LatestRecords
AS
    WITH RecordsWithNoDuplicates_CTE  AS
    (
    SELECT 
        ROW_NUMBER() OVER (PARTITION BY name Order by DateAdded DESC) AS RowNo,
        Name,
        DateAdded,
        Reason 
    FROM 
        MyTable
    )
    SELECT * FROM RecordsWithNoDuplicates_CTE WHERE RowNo=1

此视图随后可用于后续查询和函数，例如：

SELECT 
    100*Count(CASE WHEN Reason='Case1' THEN 1 ELSE NULL END)/Count(*) as Percentage
FROM LatestRecords

将使用reason =“Case1”计算最新记录的出现次数，并将其除以最新记录的总数（给出百分比）。