Question

我有两个选择的case语句，我想以某种方式合并在一起。我尝试了不同的嵌套变体，到目前为止，除了错误之外我什么都没得到。我正在使用SQL Server 2008，并希望它尽可能向后兼容SQL 2005，因为我们设置了2005年的第二个实例。

我正在做的是查看帐户的付款次数，并尝试确定它是每周，每两周，每月还是每两个月一次。

根据计划的付款次数，取决于我用于计算付款之间的天数。由于没有真正的每周，每两周等选择，我们会根据首次预定付款与上次预定付款之间的天数除以数量，使用一系列天数。付款。

以下是我的两个案例陈述：第一个给出了付款之间的天数。

    case NoPymnts
    when 1 then 0
    when 2 then (datediff(d, DueDt1, DueDt2)/NoPymnts)
    when 3 then (datediff(d, DueDt1, DueDt3)/NoPymnts)
    when 4 then (datediff(d, DueDt1, DueDt4)/NoPymnts)
    when 5 then (datediff(d, DueDt1, DueDt5)/NoPymnts)
    when 6 then (datediff(d, DueDt1, DueDt6)/NoPymnts)
    when 7 then (datediff(d, DueDt1, DueDt7)/NoPymnts)
    when 8 then (datediff(d, DueDt1, DueDt8)/NoPymnts)
    when 9 then (datediff(d, DueDt1, DueDt9)/NoPymnts)
    when 10 then (datediff(d, DueDt1, DueDt10)/NoPymnts)
    when 11 then (datediff(d, DueDt1, DueDt11)/NoPymnts)
    when 12 then (datediff(d, DueDt1, DueDt12)/NoPymnts)
    end as DayCount

这个包含决定付款频率的逻辑：

    case
    when DayCount = 0 then 'SinglePayment'
    when DayCount <=7 then 'Weekly'
    when DayCount >7 and DayCount <= 21 then 'Bi-Weekly'
    when DayCount >21 and Daycount <= 42 then 'Monthly'
    when DayCount > 42 then 'Bi-Monthly'
    End As Frequency

我知道一个可行的选项，但是大而混乱的是将第二个案例放入第一个case语句中每个选项的子案例语句中。我真的更愿意避免这种情况。我想避免的第二个选项是使用临时表。但是，如果我不能做我在这里尝试的事情，我可能会被迫使用一个。

感谢您的帮助！

Answer 1

只需将第二种情况下DayCount的值替换为您在第一种情况下使用的计算，因为您似乎在执行相同的计算而不管NoOfPymts，但单笔付款除外：

case
    when NoPymnts = 1 then 'SinglePayment'
    when (datediff(d, DueDt1, DueDt2)/NoPymnts)<=7 then 'Weekly'
    when (datediff(d, DueDt1, DueDt2)/NoPymnts)>7 
         and (datediff(d, DueDt1, DueDt2)/NoPymnts)<= 21 then 'Bi-Weekly'
    when (datediff(d, DueDt1, DueDt2)/NoPymnts)>21 
         and (datediff(d, DueDt1, DueDt2)/NoPymnts)<= 42 then 'Monthly'
    when (datediff(d, DueDt1, DueDt2)/NoPymnts)> 42 then 'Bi-Monthly'
    End As Frequency

Answer 2

为第二种情况创建用户定义的函数，如下所示

CREATE FUNCTION GetFrequencyFromDayCount 
(
    @DayCount INT
)
RETURNS VARCHAR(50)
AS
BEGIN
    DECLARE @Freq NVARCHAR(50)
    SELECT @Freq = case
    when @DayCount = 0 then 'SinglePayment'
    when @DayCount <=7 then 'Weekly'
    when @DayCount >7 and @DayCount <= 21 then 'Bi-Weekly'
    when @DayCount >21 and @DayCount <= 42 then 'Monthly'
    when @DayCount > 42 then 'Bi-Monthly'
    End 
    RETURN @Freq
END
GO

在第一个case语句中调用该函数，如下所示

select
  case NoPymnts
    when 1 then 0
    when 2 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt2)/NoPymnts))
    when 3 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt3)/NoPymnts))
    when 4 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt4)/NoPymnts))
    when 5 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt5)/NoPymnts))
    when 6 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt6)/NoPymnts))
    when 7 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt7)/NoPymnts))
    when 8 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt8)/NoPymnts))
    when 9 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt9)/NoPymnts))
    when 10 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt10)/NoPymnts))
    when 11 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt11)/NoPymnts))
    when 12 then GetFrequencyFromDayCount((datediff(d, DueDt1, DueDt12)/NoPymnts))
    end as DayCount

Answer 3

您是否只是想找到一种方法来先查找日数，然后再进行构建？然后使用派生表查询：

select
  some_column,
  other_column,
  case
    when DayCount = 0 then 'SinglePayment'
    when DayCount <=7 then 'Weekly'
    when DayCount >7 and DayCount <= 21 then 'Bi-Weekly'
    when DayCount >21 and Daycount <= 42 then 'Monthly'
    when DayCount > 42 then 'Bi-Monthly'
  End As Frequency
from
(
  select 
    some_column,
    other_column,
    case NoPymnts
      when 1 then 0
      when 2 then (datediff(d, DueDt1, DueDt2)/NoPymnts)
      when 3 then (datediff(d, DueDt1, DueDt3)/NoPymnts)
      when 4 then (datediff(d, DueDt1, DueDt4)/NoPymnts)
      when 5 then (datediff(d, DueDt1, DueDt5)/NoPymnts)
      when 6 then (datediff(d, DueDt1, DueDt6)/NoPymnts)
      when 7 then (datediff(d, DueDt1, DueDt7)/NoPymnts)
      when 8 then (datediff(d, DueDt1, DueDt8)/NoPymnts)
      when 9 then (datediff(d, DueDt1, DueDt9)/NoPymnts)
      when 10 then (datediff(d, DueDt1, DueDt10)/NoPymnts)
      when 11 then (datediff(d, DueDt1, DueDt11)/NoPymnts)
      when 12 then (datediff(d, DueDt1, DueDt12)/NoPymnts)
    end as DayCount
  from mytable
) myderivedtable;

SQL Select Case Combining

3 个答案: