Third Normal Form (3NF)
A non-key field is not a fact about another non-key field.
Reln R with FDs F is in 3NF if, for all X A in
- A X (called a trivial FD), or
- X is a superkey for R, or
- A is prime
Example: ED = (enum, ename, sal, dnum, dname, mgr)
- FDs: enum ? ename, sal, dnum and dnum ? dname, mgr
- Is ED in 2NF? 3NF?
The problem: dname, mgr stored for all employees in a department