I have
R(ABCDE) which AB is primary key and F= { f1: AB->CDE; f2: BD->E }
I'm confused because my textbook said it reached 3rd normal form but the when I checked it by the online tool, it said the relation reached 2rd form because of f2 violation.
Which is right?
Codd's definition of 3NF includes the stipulation that every non-prime attribute of a table is non-transitively dependent on every key.
In other words, since E is dependent both on (AB) and (BD) but C is only dependent on (AB), this is a 3NF violation.
The online tool is right.
To make this 3NF you need to break into two relations: ABCD and BDE. However this poses issues relating to referential integrity enforcement.