Dynamically changing searches based on the given parameters is a complicated subject and doing it one way over another, even with only a very slight difference, can have massive performance implications. The key is to use an index, ignore compact code, ignore worrying about repeating code, you must make a good query execution plan (use an index).
Read this and consider all the methods. Your best method will depend on your parameters, your data, your schema, and your actual usage:
If you have the proper SQL Server 2008 version (SQL 2008 SP1 CU5 (10.0.2746) and later), you can use this little trick to actually use an index:
OPTION (RECOMPILE) onto your query, see Erland's article, and SQL Server will resolve the
OR from within
(@LastName IS NULL OR LastName= @LastName) before the query plan is created based on the runtime values of the local variables, and an index can be used.
This will work for any SQL Server version (return proper results), but only include the OPTION(RECOMPILE) if you are on SQL 2008 SP1 CU5 (10.0.2746) and later. The OPTION(RECOMPILE) will recompile your query, only the verison listed will recompile it based on the current run time values of the local variables, which will give you the best performance. If not on that version of SQL Server 2008, just leave that line off.
CREATE PROCEDURE spDoSearch @FirstName varchar(25) = null, @LastName varchar(25) = null, @Title varchar(25) = null AS BEGIN SELECT ID, FirstName, LastName, Title FROM tblUsers WHERE (@FirstName IS NULL OR (FirstName = @FirstName)) AND (@LastName IS NULL OR (LastName = @LastName )) AND (@Title IS NULL OR (Title = @Title )) OPTION (RECOMPILE) ---<<<<use if on for SQL 2008 SP1 CU5 (10.0.2746) and later END