SQL - Conditional WHERE clause

Question

I have a SQL Server 2005 stored procedure that performs a query. This stored procedure takes in three parameters. The parameters are as follows:

@Stat

Answer 1

there is no "right way", it depends on many factors, here is a great article describing the PROs and CONs of each way to have dynamic search conditions:

http://www.sommarskog.se/dyn-search.html

Answer 2

One way:

SELECT * 
FROM Customer c 
WHERE c.StateID=@StateID 
    AND (@CountyID IS NULL OR c.CountyID=@CountyID)
    AND (@CityID IS NULL OR c.CityID=@CityID)

Another way:

SELECT * 
FROM Customer c 
WHERE c.StateID=@StateID 
    AND c.CountyID=ISNULL(@CountyID, c.CountyID)
    AND c.CityID=ISNULL(@CityID, c.CityId)

Answer 3

SELECT * 
FROM Customer c 
WHERE c.StateID=@StateID 
AND c.CountyID= ISNULL(@CountyID, c.CountyID) 
AND c.CityID = ISNULL(@CityID, c.CityID)

Answer 4

 SELECT * FROM Customer c WHERE (c.StateID=@StateID) AND ((c.CountyID=@CountyID) OR (@CountyID IS NULL)) AND ((c.CityID=@CityID) OR (@CityID IS NULL))

Answer 5

Try it with coalesce, I think it's a very elegant, clean approach:

SELECT *
FROM Customer c
WHERE
 c.StateID=@StateID 
 AND c.CountyID = COALESCE(@CountyID, c.CountyID)
 AND c.CityID = COALESCE(@CityID, c.CityID)

(Be aware though - this will filter out records with nulls in CountyID or CityID.)

Answer 6

Couple those with some OR statements:

SELECT *
FROM
    Customer c
WHERE
    c.StateID=@StateID
    AND ( c.CountyID=@CountyID OR @CountyID IS NULL )
    AND ( c.CityID=@CityID OR @CityID IS NULL )

For each of those parameters, if it is null, then the check is basically ignored.