Looking for good reference materials for SQL programming. - Mailing list pgsql-novice

I have been playing with postgresql for a while and have a copy of the book Postgresql on order.

Are there any good reference materials available to teach how to do effective SQL and relational database design. I
wouldprefer something more platform neutral but covers the theroy and concepts of good database design. Does anyone
herehave any suggestions for such materials? 

Thanks in advance.