Subject Helen: Low Selectivity Problem
Author Scronkey
Hi Helen,

I was just reading your reply (in IBObjects group) to the Data
Integrity post, and in it you mentioned that if a lookup table has
few records compared to the main table, do not use formal foreign
keys as this will give poor performance.

I do not understand this at all, as that is how I thought things
were to be setup for the purpose of referential integrity.

I have quite a few lookups (about 10), each with between 2 - 10
records, which all reference about 10 other large tables in my db.

Could you please explain why this will give poor performance, and
what the best way to maintain referential integrity will be if I am
not to use formal foreign keys?