Thanks the on & off-list replies, but I obviously didn't explain my situation very
My app is essentially creating summary reports from large amounts of data. It is _not_
doing the actual data warehousing. It's international trade data.
The data tables contain foreign keys for stuff like destination country, trade commodity
category etc., but they are _not_ themselves referenced by any other table. Therefore I
have not yet found, nor do I envisage finding, any use for an arbitrary auto_increment
primary key. So why would/might I need a PK at all?