Question

这就是我正在做的事情：

while (@counter < 3 and @newBalance >0)
begin   
CASE
when  @counter = 1 then  ( @monFee1 = @monthlyFee, @newBalance = @newBalance-@fee)
when  @counter = 2 then  ( @monFee2 = @monthlyFee, @newBalance = @newBalance-@fee)
END
@counter = @counter +1
end

我收到此错误：

关键字'CASE'附近的语法不正确。

不知道为什么。请帮忙！

Answer 1

对于你提出的建议，你应该使用IF语句

While (@counter < 3 and @newBalance >0)
Begin
    If @Counter = 1 Then
        Begin
            Set @monFee1 = @monthlyFee
            Set @newBalance = @newBalance-@fee
        End

    If @Counter = 2 Then
        Begin
            Set @monFee2 = @monthlyFee
            Set @newBalance = @newBalance-@fee
        End

    Set @counter = @counter +1 
End

Answer 2

不，SQL中的CASE结构是返回一个值，而不是程序流。您需要将其分解为IF语句。

Answer 3

CASE语句不像处理程序代码中的表兄一样用于分支逻辑。它将在结果集中返回结果，以便在为变量赋值时，可以确定该值不是您要分配给哪个变量的值。

不幸的是，

(@monFee1 = @counter, @newBalance = @newBalance-@fee)

不会返回值。

使用If / Else bracnching逻辑的另一种方法是

while (@counter < 3 and @newBalance >0)
begin   
    IF @counter = 1
    THEN
        SET @monFee1 = @monthlyFee
        SET @newBalance = @newBalance-@fee
    END
    ELSE IF @counter = 2
    BEGIN
        SET @monFee2 = @monthlyFee
        SET @newBalance = @newBalance-@fee
    END
        SET @counter = @counter +1
end

Answer 4

你不应该在这里使用while循环。您实际上只检查@newBalance的值一次。考虑：

@monFee1 = @monthlyFee
@newBalance = @newBalance-@fee

IF @newBalance > 0
BEGIN
   @monFee2 = @monthlyFee
   @newBalance = @newBalance-@fee
END

Answer 5

由于CASE是一个表达式，您可以在SET赋值语句中使用它。

WHILE (@counter < 3 and @newBalance >0) 
BEGIN
  SET @monFee1 = CASE WHEN @Counter=1
    THEN @monthlyFee ELSE @monFee1 END
  SET @monFee2 = CASE WHEN @Counter=2
    THEN @monthlyFee ELSE @monFee2 END
  SET @newBalance = @newBalance - CASE WHEN @Counter in (1, 2)
    THEN @fee ELSE 0 END
  SET @counter = @counter +1 
END

它也可以在SELECT赋值语句中。

WHILE (@counter < 3 and @newBalance >0) 
BEGIN
  SELECT
    @monFee1 = CASE WHEN @Counter=1
      THEN @monthlyFee ELSE @monFee1 END,
    @monFee2 = CASE WHEN @Counter=2
      THEN @monthlyFee ELSE @monFee2 END,
    @newBalance = @newBalance - CASE WHEN @Counter in (1, 2)
      THEN @fee ELSE 0 END,
    @counter = @counter +1 
END

PS：祝你的老龄化报告好运......

我可以在WHILE循环中使用CASE语句吗？

5 个答案: