I have an impedance mismatch problem, namely a model in X categories,
each having its own set of fields and all having a set of common fields.
I solved that with:
1. master table, contains the sequenced pkey and common fields, as
well as category discriminator
2. individual category tables
Ah, a solution just came to me. If I had 10 categories and denormalized
the user_id into them, I can reverse the queries and do only 10 selects,
filtered by user_id and joined with the master table on pkey. I'd end up
with equal number of rows selected, but only 10 queries issued. The
