如果聲明內部案例嵌入

Question

如何在案例中嵌入和if語句。 這就是我到目前為止所擁有的。

DECLARE @LDCCode as int
       DECLARE @InvoiceDate as datetime
       DECLARE @PaymentSemiMonthlyDays AS int
       SET @LDCCode = 20
       SET @InvoiceDate = '5/16/2012'
       DECLARE @InvDateDayMonth AS INT
       DECLARE @ReturnDate AS DATETIME
       SET @ReturnDate = @InvoiceDate
       DECLARE @PaymentDOM AS INT
       DECLARE @PaymentDays AS INT
       DECLARE @PaymentSemiMonthlyOffset AS INT


SET @ReturnDate = CASE WHEN NOT @PaymentDOM IS NULL THEN
   @ReturnDate + (@PaymentDOM - DATEPART(day, DateAdd(mm,1,@ReturnDate))) 
WHEN NOT @PaymentDays IS NULL THEN 
            DATEADD(Day,@PaymentDays,@ReturnDate)
WHEN NOT @PaymentSemiMonthlyOffset IS NULL THEN                     
    IF @LDCCode = 40 AND @InvDateDayMonth > 11 AND @InvDateDayMonth < 26 
       SELECT @ReturnDate + (@PaymentSemiMonthlyOffset - DATEPART(day, DateAdd(mm,1,@ReturnDate)))
    ELSE
       SELECT @ReturnDate + (@PaymentSemiMonthlyDays - DATEPART(day, DateAdd(mm,1,@ReturnDate)))    
    END 

Answer 1

您不能以這種方式組合邏輯，但您可以在現有CASE語句中添加嵌套CASE ：

SET @ReturnDate = (CASE WHEN NOT @PaymentDOM IS NULL THEN
    @ReturnDate + (@PaymentDOM - DATEPART(day, DateAdd(mm,1,@ReturnDate))) 
WHEN NOT @PaymentDays IS NULL THEN 
    DATEADD(Day,@PaymentDays,@ReturnDate)
WHEN NOT @PaymentSemiMonthlyOffset IS NULL THEN
    CASE WHEN @LDCCode = 40 AND @InvDateDayMonth > 11 AND @InvDateDayMonth < 26 THEN
        @ReturnDate + (@PaymentSemiMonthlyOffset - DATEPART(day, DateAdd(mm,1,@ReturnDate)))
    ELSE
        @ReturnDate + (@PaymentSemiMonthlyDays - DATEPART(day, DateAdd(mm,1,@ReturnDate)))
    END   
END)

但是，如果這是在存儲過程中，我可能只選擇更簡單的IF/THEN/ELSE結構而不是CASE ：

IF @PaymentDOM IS NULL
    SET @ReturnDate = @ReturnDate + (@PaymentDOM - DATEPART(day, DateAdd(mm, 1, @ReturnDate))) 
ELSE IF NOT @PaymentDays IS NULL
    SET @ReturnDate = DATEADD(Day,@PaymentDays,@ReturnDate)
ELSE IF NOT @PaymentSemiMonthlyOffset IS NULL
BEGIN
    IF @LDCCode = 40 AND @InvDateDayMonth > 11 AND @InvDateDayMonth < 26
        SET @ReturnDate = @ReturnDate + (@PaymentSemiMonthlyOffset - DATEPART(day, DateAdd(mm, 1, @ReturnDate)))
    ELSE
        SET @ReturnDate = @ReturnDate + (@PaymentSemiMonthlyDays - DATEPART(day, DateAdd(mm, 1, @ReturnDate)))
END

Answer 2

由於所有表達式都向@ReturnDate添加了一些@ReturnDate ，並且由於您在@ReturnDate之后多次計算了一個月的@ReturnDate ，因此我認為這可以簡化為：

DECLARE @Plus1M INT;
SET @Plus1M = DATEPART(DAY, DATEADD(MONTH, 1, @ReturnDate));

SET @ReturnDate = DATEADD(DAY, 
  COALESCE(
    @PaymentDays, -- if @PaymentDays IS NULL, this will be skipped
    @PaymentDOM - @Plus1M,  -- if @PaymentDOM is NULL, this will be skipped
    CASE WHEN @PaymentSemiMonthlyOffset IS NOT NULL THEN
      CASE WHEN @LDCCode = 40 AND @InvDateDayMonth BETWEEN 12 AND 25
        THEN @PaymentSemiMonthlyOffset 
        ELSE @PaymentSemiMonthlyDays 
      END - @Plus1M
    END
  ), 
  @ReturnDate
);

但是如果你想把它寫成冗長和冗余的表達式，那么：

SET @ReturnDate = CASE 
  WHEN @PaymentDOM IS NOT NULL THEN
    DATEADD(DAY, @PaymentDOM 
    - DATEPART(DAY, DATEADD(MONTH, 1, @ReturnDate)), @ReturnDate) 
  WHEN @PaymentDays IS NOT NULL THEN 
    DATEADD(DAY, @PaymentDays, @ReturnDate)
  WHEN @PaymentSemiMonthlyOffset IS NOT NULL THEN
    CASE WHEN @LDCCode = 40 AND @InvDateDayMonth BETWEEN 12 AND 25 THEN
      DATEADD(DAY, @PaymentSemiMonthlyOffset 
      - DATEPART(DAY, DATEADD(MONTH, 1, @ReturnDate)), @ReturnDate)
    ELSE
      DATEADD(DAY, @PaymentSemiMonthlyDays 
      - DATEPART(DAY, DATEADD(MONTH, 1, @ReturnDate)), @ReturnDate)   
    END 
  END;

雖然很難驗證，因為您現有的查詢沒有解析，並且您沒有向我們展示樣本數據或期望的結果。

我會避免使用@Datetime + INT速記，而是拼出DATEADD操作，因為速記不適用於較新的類型（ DATE ， DATETIME2等）。 我也避免使用mm這樣的速記，因為這些縮寫中有幾個是不明顯的。 另外三個字符使得更加明顯。 還有NOT ...something... IS NULL讀起來不是很直觀。 我寧願說“光不是紅”而不是“不是光是紅的”。