"Jamie Collins" wrote in
oups.com:

Just another thought: alarm bells ring in my head when I see a single
column table. That's why my notes say, if the colours rarely change
then just use:

ALTER TABLE Cars ADD CHECK (car_colour IN ('Red', 'White', 'Blue'));


Do you have any authoritative reference for these alarm bells? I don't
know of any reason within R theory to avoid one-column tables, or any
other kind of all-PK tables.

This design could work if you _knew_ that the colours would _never_,
_ever_ change. It is used sometimes, for example with Gender; but even
then it's something of a short cut.

All the best


Tim F