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

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.)