Below is a link to a basic overview of using SQL in FileMaker. It is work in progress and being added to but may give some low level SQL users a bit more of an insight, from my experience working with SQL. If you know of anyone who would make use of this, please forward it on.
http://fmforums.com/forum/files/file/47-filemaker-sql-basic-overviewpdf/
Hope it helps,
Jamie L. Thompson.