CASE什麼時候在哪裏條款？

Question

我有一個有趣的問題。我將寫一個標量值函數。其中一個參數不在表格列中。我必須在where子句中使用此參數（@ImpUrgPri）。至於該參數，表中存在列的條件。你能幫我解答嗎？

DECLARE @ImpUrgPri NVARCHAR(3) 
SET @ImpUrgPri = 'URG' 
DECLARE @Enum INT 
SET @Enum = 0 

select COUNT(*) 
from zODYA_vwCallReq_AllData 
where ActiveFlag = 1 
AND 
(CASE WHEN (@ImpUrgPri = 'PRI') THEN Priority_Enum == @Enum 
     WHEN (@ImpUrgPri = 'URG') THEN Urgency_Enum == @Enum 
     WHEN (@ImpUrgPri = 'IMP') THEN Impact_Enum == @Enum END) 

group by 
(CASE WHEN (@ImpUrgPri = 'PRI') THEN Priority_Enum 
     WHEN (@ImpUrgPri = 'URG') THEN Urgency_Enum 
     WHEN (@ImpUrgPri = 'IMP') THEN Impact_Enum END) 

Answer 1

你的選擇可能是因爲：

select COUNT(*) 
from zODYA_vwCallReq_AllData 
where ActiveFlag = 1 
AND @Enum = (CASE WHEN (@ImpUrgPri = 'PRI') THEN Priority_Enum 
      WHEN (@ImpUrgPri = 'URG') THEN Urgency_Enum 
      WHEN (@ImpUrgPri = 'IMP') THEN Impact_Enum END) 

group by 
(CASE WHEN (@ImpUrgPri = 'PRI') THEN Priority_Enum 
     WHEN (@ImpUrgPri = 'URG') THEN Urgency_Enum 
     WHEN (@ImpUrgPri = 'IMP') THEN Impact_Enum END) 

Answer 2

我認爲這將是最好使用IF，並有三種不同的SELECT S，爲每個「時」的情況。

您也可以動態地創建SQL（在存儲過程中），這會使存儲過程稍微短一些。在這裏只有三個選項，我會堅持3個選擇。

Answer 3

DECLARE @ImpUrgPri NVARCHAR(3) 
SET @ImpUrgPri = 'URG' 
DECLARE @Enum INT 
SET @Enum = 0 

select COUNT(*) 
from zODYA_vwCallReq_AllData 
where ActiveFlag = 1 
AND 
(CASE @ImpUrgPri 
    WHEN 'PRI' THEN Priority_Enum 
    WHEN 'URG' THEN Urgency_Enum 
    WHEN 'IMP' THEN Impact_Enum 
END) = @Enum 
group by 
(CASE @ImpUrgPri 
    WHEN 'PRI' THEN Priority_Enum 
    WHEN 'URG' THEN Urgency_Enum 
    WHEN 'IMP' THEN Impact_Enum 
END)