answer fa f reflexivity c fa given and fa f imply c f

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: swer: FA F (reflexivity) C FA (given) and FA F imply C F (transitivity) AB C (given), C F and F E (given) imply AB E (transitivity) Q.9 [20 pts] Consider the relation schema R(A, B, C, D) and the following functional dependencies that hold on R: A BC, B C (a) [5 pts] Find the candidate key(s). (b) [5 pts] Show that R is not in 3NF. (c) [10 pts] Find a lossless-join, dependency-preserving decomposition of R into 3NF. Answer: (a) The only candidate key is AD. (b) For the dependency B C it holds that (i) it is not trivial; (ii) B is not a superkey for R; (iii) C is not contained in a candidate key. This shows that R is not in 3NF. (We could also have used the dependency A A C.) B, or (c) We first construct a canonical cover of the dependencies: {A B, B C}. The algorithm in the textbook results in the decomposition {AB, BC, AD} where AD has to be added since neither AB nor BC contains a candidate key. (If the original dependencies, rather than the canonical cover, is used, the decomposition algorithm would have produce {ABC, AD} where ABC is not in 3NF, due to the dependency B C.)...
View Full Document

This homework help was uploaded on 03/08/2014 for the course CS 352 taught by Professor Özgürulusoy during the Spring '11 term at Bilkent University.

Ask a homework question - tutors are online