The "Microsoft Jet SQL for Access 2000" papers (from Shadow's linked page) are good (if you don't mind me shadowing Shadow). If they're not quite what you had in mind, you may also want to download a few sample DBs from this forum in the Sample Databases section -- the DBs that deal with a combo- or listbox will often involve SQL strings. Also, if you have the time, browse through the Help file, searching on rowsource and recordsource, two properties that accept SQL strings. A good book can go a long way too -- the Access Developers Handbook is pricey but valuable if you think you will be using Access and VBA. There are other book recommendations scattered over these forums; I recall one post from Pat Hartman (one of the many Access mavens here) in which she listed at least a half dozen different titles, providing a one or two sentence description for each...
Regards,
Tim