I think that we (r937, stolze, and I) are all recommending the same thing, using very slightly different language.

Joe Celko's SQL For Smarties book is nothing short of excellent in my opinion. The concepts and topics that are covered are beyond what the average LAMP programmer will need, but they are the bread-and-buter of the extrordinary programmer! Reading SQL For Smarties and learning what Joe has to offer is an excellent use of your time.

ANSI/ISO SQL is the standard which EVERY SQL database engine should implement. While most vendors will choose to incorporate extensions to the standard (many of which are often then incorporated into later versions of the standard), I think that if a vendor chooses not to include full ANSI/ISO standard support, then they should be required to footnote their use of the term SQL to indicate what standard features they've chosen not to support!

-PatP