Originally posted by Aus1423
So basically foreign keys aren't unique to the entire column but just to specific values? Is this what you guys are saying?

Say for instance an entire column of foreign keys in a table is seen as primary keys in another table (displayed in the same order no less) then they should all be NOT NULL values. But take a totally separate unrelated table that has foreign keys with alot of NULLs, so can that column not have ANY reference to another table? Seems they shouldn't.

I can't see using some foreign keys for another table and not others if there are NULLs. I'm used to seeing an entire column of attributes being used as primary keys in another table. Thats why I'm confused.

Should I look at it like the entire column is referenced or is NULL or just as individual values being one or the other?
being nullable and being keys into other tables are somewhat seperate issues.

You can also have both, and you can have value oriented constraints on tables (which programmers hate but DBAs sometimes like).