yeah, I hadn't suggested to add the AND to the default where because I did not realize yu had another condition already in place for the where clause, this is why the full page code is often key.
I'm not sure I follow what you mean by "when to use what in the search's WHERE" Do you mean the default where?
If you asking about the default where, there really isn't a guide on what to use and when to use it outside of the SQL documentation. it very much depends on the results you wish to accomplish.