>Are you saying that the Where clause I posted ("where Col_IntType = COALESCE(@param1, Col_IntType)" will not return records with NULL value? Why not? If @param1 is NULL than the expression will evaluate to Col_IntType = Col_IntType; and wouldn't it be always True regardless of the value in the field?

Read this excellent article for in depth discussion http://www.sommarskog.se/dyn-search-2008.html