SQL - 有条件地评估WHERE子句

Question

我需要获取WHERE子句才能评估某些语句。例如：

WHERE field_a = field_b AND 
    (CASE WHEN <PARAM>type</PARAM> = 5 
     THEN {field_c = 1 OR field_c = 2} 
     WHEN <PARAM>type</PARAM> = 6 
     THEN {field_c = 3 OR field_c = 4} 
     ELSE field_c = <PARAM>type</PARAM> 

因此，当参数类型= 5时，它只会检查field_c = 1或2.是否有想法？

Answer 1

WHERE field_a = field_b 
AND (
    (type = 5 AND (field_c = 1 OR field_c = 2)) 
    OR (type = 6 AND (field_c = 3 OR field_c = 4)) 
    OR field_c = type 
) 

这就是你所追求的？

Answer 2

WHERE 
((field_a = field_b)) AND 
(((<PARAM>type</PARAM> = 5) AND (field_c IN (1, 2))) OR 
((<PARAM>type</PARAM> = 6) AND (field_c IN (3, 4))) OR 
((<PARAM>type</PARAM> NOT IN (5, 6) AND <PARAM>type</PARAM> = field_c))) 

Answer 3

这样做吗？

Where field_a = field_b AND 
(
    (<PARAM>type</PARAM> = 5 AND field_c IN (1,2)) 
    OR (<PARAM>type</PARAM> = 6 AND field_c IN (1,2)) 
    OR (field_c = <PARAM>type</PARAM>) 
) 

Answer 4

这是我想到的，从帖子的一些灵感后，我意识到我不需要这样的条件代码。此外，Param类型可以接受多个值，并以逗号分隔输出它们，这非常有帮助。

WHERE field_a = field_b AND 
    (field_c in (<PARAM>type</PARAM>)) 

感谢您的帮助！

Answer 5

WHERE field_a = field_b AND 
     CASE WHEN <PARAM>type</PARAM> = 5 THEN 
       CASE WHEN field_c = 1 OR field_c = 2 THEN 1 ELSE 0 END 
      WHEN <PARAM>type</PARAM> = 6 THEN 
       CASE WHEN field_c = 3 OR field_c = 4 THEN 1 ELSE 0 END 
      ELSE 
       CASE WHEN field_c = <PARAM>type</PARAM> THEN 1 ELSE 0 END 
     END = 1