good sql tutorial

Anyone have a recommendation for a good sql tutorial?  Looking for a
book, but online would be useful as well.

This is for a financial user who will need to have an understanding of
sql in order to generate reports with a report writer like openrpt.

Thanks for any suggestions.

--
Until later, Geoffrey

Those who would give up essential Liberty, to purchase a little
temporary Safety, deserve neither Liberty nor Safety.
  - Benjamin Franklin