IN CASE THEN表達式中的結果表達式中的IN語句

Question

可以在CASE..THEN中使用IN嗎？

WHERE 
    record.field = 
     CASE 
      WHEN @flag = 1 THEN a 
      WHEN @flag = 2 THEN IN (b, c) 
     END 

或者如何改寫這樣的條件？

Answer 1

對不起，沒有：

WHERE 
    (@flag = 1 AND record.field = a) 
    OR 
    (@flag = 2 AND record.field IN (b, c)) 

Answer 2

嘗試：

WHERE (@flag = 1 AND record.field = a) 
    OR (@flag = 2 AND record.field IN (b, c)) 

它可能是更好地嘗試在價值加入並使用索引：

DECLARE @Table (ValueOf int) 
INSERT INTO @Table ((ValueOf) 
    SELECT a WHERE @flag = 1 
    UNION SELECT b WHERE @flag = 2 
    UNION SELECT c WHERE @flag = 2 

SELECT 
    .... 
    FROM ...   x 
    INNER JOIN @Table t ON x...=t.ValueOf