Question

我一直试图将当前和以前的记录检索为一行。我需要在当前记录之前获得直接记录，以比较两行的位置。

Select 
    CurrentMovement.Location, CurrentMovement.EffectiveDate
  , PreviousMovement.Location, PreviousMovement.EffectiveDate 
From Product product
Inner join ProductMovement CurrentMovement ON product.Id = CurrentMovement.ProductId
    And CurrentMovement.EffectiveDate = (Select Max(EffectiveDate)
                                         From ProductMovement
                                         Where ProductId = product.ProductId)
Inner join ProductMovement PreviousMovement ON PreviousMovement.ProductId = CurrentMovement.ProductId
    And PreviousMovement.EffectiveDate < CurrentMovement.EffectiveDate
Where CurrentMovement.Locations != PreviousMovement.Location

我能够在CurrentMovement内连接上检索当前记录。

问题是确定下一个内部联接的上一个记录，因为我需要检索小于CurrentMovement.EffectiveDate的先前记录的Max（EffectiveDate）。

感谢您的帮助。

Answer 1

诀窍是分配顺序行号并使用此行号连接。像这样：

WITH PM AS(
    SELECT *
        , RN = ROW_NUMBER() OVER(PARTITION BY ProductId ORDER BY EffectiveDate DESC)
    FROM ProductMovement
)
Select 
    PMC.Location, PMC.EffectiveDate
  , PMP.Location, PMP.EffectiveDate 
From Product AS P
    INNER join PM AS PMC
        ON P.Id = PMC.ProductId
        AND PMC.RN = 1
    LEFT JOIN PM ON PMP
        ON P.Id= PMP.ProductId
        AND PMP.RN - 1 = PMC.RN

SQL执行自联接以按日期检索当前和前一个记录

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