CP363 Lecture Notes - Lecture 21: Third Normal Form, Superkey, Second Normal Form
8 Apr 2019
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Definition : transitive functional dependency : a fd x->z. Since there is no set of attributes x where ssn->x and x->ename. 4. 1 general definition of 2nf is in second form (2nf) if every non prime attribute a in r is fully functionally dependent. Superkey of relation schema r- a set of attributes s of r that contains a key of. A relation schema r is in third normal form(3nf), if whenever a fd x-> holds in. (a) x is a superkey of r or. (b) a is a prime attribute of r. Area->price and area is not a superkey in lots1 ( see figure 14. 12) Condition (a) catches two types of violations: bcnf (boyce-codd normal form) A relation schema r is in bcnf if whenever an fd x->a holds in r then x is a superkey of r. Each normal form is strictly stronger than the previous one. There exist relations that are in 3nf but not in bcnf.
