SQL 循环检查

Question

我在创建 SQL 查询时遇到了一个小问题。我有一个 table 有 4 列 'Enquiry Date' , 'Taken Date' , 'Indication Date' , 'Cancelled Date' table 被称为 tbl_Sales.

我想做的是创建一个 t-sql 来表示查看 4 列，日期最接近 GETDATE() 的就是当前状态。

因此，例如，如果该行在每一列中都有一个日期，并且填写的最后日期是昨天在 'Cancelled Date' 中，那么该行的状态应显示为 canceled。

可以这样做吗？

Answer 1

如果你没有一些状态字段，你的设计就很糟糕。这是暴力解决方案：

SELECT  *,
        CASE WHEN [Cancelled Date] IS NOT NULL AND 
                  ([Cancelled Date] > [Indication Date] OR [Indication Date] IS NULL) AND
                  ([Cancelled Date] > [Taken Date] OR [Taken Date] IS NULL) AND
                  ([Cancelled Date] > [Enquiry Date] OR [Enquiry Date] IS NULL) THEN 'Canceled'
             WHEN [Indication Date] IS NOT NULL AND 
                  ([Indication Date] > [Cancelled Date] OR [Cancelled Date] IS NULL) AND
                  ([Indication Date] > [Taken Date] OR [Taken Date] IS NULL) AND
                  ([Indication Date] > [Enquiry Date] OR [Enquiry Date] IS NULL) THEN 'Indication'        
             WHEN [Taken Date] IS NOT NULL AND 
                  ([Taken Date] > [Indication Date] OR [Indication Date] IS NULL) AND
                  ([Taken Date] > [Cancelled Date] OR [Cancelled Date] IS NULL) AND
                  ([Taken Date] > [Enquiry Date] OR [Enquiry Date] IS NULL) THEN 'Taken'        
             WHEN [Enquiry Date] IS NOT NULL AND 
                  ([Enquiry Date] > [Indication Date] OR [Indication Date] IS NULL) AND
                  ([Enquiry Date] > [Taken Date] OR [Taken Date] IS NULL) AND
                  ([Enquiry Date] > [Cancelled Date] OR [Cancelled Date] IS NULL) THEN 'Enquiry'        
        END            
FROM Sales

编辑：

这里是一些简化版：

SELECT  *
FROM    Sales
        CROSS APPLY ( SELECT TOP 1
                                st
                      FROM      ( VALUES ( [Enquiry Date], 'Enquiry'),
                                ( [Taken Date], 'Taken'),
                                ( [Indication Date], 'Indication'),
                                ( [Cancelled Date], 'Canceled') ) d ( dt, st ) 
                      ORDER BY dt DESC
                    ) ca

SQL 循环检查

SQL loop through check

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