Functional dependencies and Normalization

consider a relation R = {P, Q, R, S, T} and the functional dependency F = {P -> Q, {Q, R} -> S, S -> {Q, R}, {S, T} -开发者_开发知识库> phi}. Are there any redundant functional dependencies in F? If so, remove them and decompose the relation R to 3NF relation.

Plz answer this

{S,T}->phi is trivial, and hence redundant. Moreover, there are no redundant attributes so you have your canonical cover here.

To decompose to 3NF you should:

1) create table for each dependency in the canonical cover

2) identify a candidate key

3) if the candidate key is not included in any of the tables so far, add it as an additional table

4) remove tables if all their attributes are included in another table