Just a quick notice about the LEN function in SQL Server 2000 and 2005 (at least, haven't looked at 2008 yet).
But an often overlooked “feature” of LEN is that the function trims trailining spaces, so a LEN('a ') will return 1.
However if you reverse it and use LEN(' a') it’ll return 2.

This is something which can cause problems/issues at times, if not paying attention to the documentation.