The following table :
EmpId State Zip
1 FL 342008
2 CA 342001
is not in 3rd normal form because State is dependent on the primary key(EmpId) transitively.
So, if I break it like this : (EmpId,State) (State,PIN)
it's in 3NF.
I could also break it like : (EmpId,State) (EmpId,PIN) and it will again be in 3NF.
But in the second case, there is redundancy of information, for e.g.
1 FL
2 FL
1 342008
2 342008
Which property does the second decomposition violate?
-
This doesn't directly address your question, but, strictly speaking, the state column is redundant, because it can be derived from the ZIP code (although you're showing six-digit ZIP codes, which aren't standard in the USA.) You could break the table down by EmpID and ZIP, leaving State by itself in a lookup table.
-
As already said, there is redundancy because the State can be inferred by the ZIP Code, hence, you should have your tables in this way:
EmpId Zip 1 342008 Zip State 342008 FLAlways think on what depends on what. Of course, there is already an standard process to normalize based on set theory. This could help you too.
-
To directly address the question asked, the violated property is FFD (full functional dependency on the key).
0 comments:
Post a Comment