Database Normalization

Functional dependency (FD) X----------> Y         means that if
there is only one  possible  value of  Y for every value of X, then
Y is Functionally dependent on X.

• Functional Dependency is “good”.  With functional dependency the primary key (Attribute A) determines the value of all the other non-key attributes (Attributes B,C,D,etc.)

• Transitive dependency is “bad”.  Transitive dependency exists if the primary/candidate key (Attribute A) determines non-key Attribute B, and Attribute B determines non-key Attribute C.

• If a relation schema has more than one key, each is called a candidate key

• An attribute in a relation schema R is called prim if it is a member of some candidate key of R