Question

如何在案例中嵌入和if语句。这是我到目前为止所做的。

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

您不能以这种方式组合逻辑，但您可以添加嵌套CASE现有的CASE语句：

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，如果这是在存储过程中，我可能只选择更简单的IF/THEN/ELSE结构而不是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

由于所有表达式都向@ReturnDate添加了一些内容，并且由于您多次计算@ReturnDate之后的一个月中的某一天，因此我认为这可以简化为：

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
);

但是如果你想把它写成详细和冗余的表达式，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;

很难验证，因为您现有的查询没有解析，而且您没有向我们展示样本数据或所需的结果。

我会避免使用@Datetime + INT简写，而是拼出DATEADD次操作，因为速记不适用于较新的类型（DATE，DATETIME2等）。我也会避免像mm这样的简写，因为其中一些缩写是不明显的。另外三个字符使得更加明显。此外，NOT ...something... IS NULL的阅读也不是很直观。我宁愿说“光不是红色”而不是“光不是红色。”

如果声明内部案例嵌入

2 个答案: