Rory,
> However your analysis has made me think much more deeply about how the
> joins work and whether or not I need left outer joins. More than that,
> the difficulty I've had explaining the database structure to you means
> that I should carefully reconsider it.
Sure. Although sometimes a very good, well-normalized structure is impossible
to explain without a clearer diagram than you can do in ASCII -- and without
a clear understanding of what the database is for.
--
Josh Berkus
Aglio Database Solutions
San Francisco