根据输入参数添加/删除where子句条件

Question

How can I add/remove an "And" condition from Where clause based on Input parameter?

If InpParm = "A" then
    Select * from Table1
           Where Field1 = "AAA"
             And Field2 = "BBB"
             And Field3 = "CCC"  

If InpParm = "B" then
    Select * from Table1
           Where Field1 = "AAA"
             And Field3 = "CCC"  

Can this be done by case statement.

Answer 1

You can create the same behavior with a series of logical operators:

SELECT *
FROM   table1
WHERE  (inpparm = 'A' AND field1 = 'AAA' AND field2 = 'BBB' AND field3 = 'CCC') OR
       (inpparm = 'B' AND field1 = 'AAA' AND field3 = 'CCC')

Note that since the conditions on field1 and field3 are identical, they could be extracted outside the or :

SELECT *
FROM   table1
WHERE  field1 = 'AAA' AND
       field3 = 'CCC' AND
       ((inpparm = 'A' AND field2 = 'BBB') OR (inpparm = 'B'))

Answer 2

SELECT *
FROM
    Table1
WHERE
    Field1 = 'AAA'
    AND Field3 = 'CCC'
    AND ((InpParm = 'A' AND Filed2 = 'BBB') or InpParm = 'B')

Mureinik was on the money as far as how your criteria can be combined but there is one fairly big issue with which is the final line of criteria needs to be in parenthesis because AND has a higher level of precedence than OR . So without wrapping the last statement in parenthesis the statement would have evaluated the all of the criteria of the ANDs together and then simply said OR InpParm = 'B' which would mean you could get Field1/2/3 results other than what was desired.

You could also note if InpParam can only have the values of 'A' OR 'B' then you wouldn't actually need the InpParm = 'A' either but for good measure I have added it.

And just because you specifically asked about whether it could be done in a case expression the answer is yes you can do whatever you want in a case expression it just isn't necessary for this particular case .

SELECT *
FROM
    Table1
WHERE
    (CASE
       WHEN InpParm = 'A' AND Field1 = 'AAA' AND Field2 = 'BBB' AND Field3 = 'CCC' THEN 1
       WHEN InpParm = 'B' AND Field1 = 'AAA' AND Field2 = 'CCC' THEN 1
       ELSE 0
    END) = 1