Answer by KillerDBA ·
There's a good Wiki article on Codd's rules:
I believe Oracle supports a solid majority of the rules.
Some people say Oracle violates rule 6. I think Oracle violates rule 3 (empty string is impossible to discern from null? Or am I mistaken?). I wouldn't be surprised if there were facilities in it to violate rule 12 (every other RDBMS I've worked with includes cheats!).
I don't know of any definitive list of Oracle capability vs the rules. Why not ask your Oracle salesperson? Let him earn his commission check.