Task 4: Consider the relation schema R(A, B, C, D, E) with the following FDs FD1: {A,B,C} → {D,E} FD2: {B,C,D} → {A,E} FD3: {C} → {D} a) Show that R is not in BCNF. Ans) X = {C} then X+ = {C, D} which is not R therefore X is not a superkey, so R is not in BCNF. b) Decompose R into a set of BCNF relations (describe the process step by step). Ans) FD3 violates BCNF. Decomposing R using FD3. R1(C,D) with FDs: FD3, CK: {C} R2(A,B,C,E) with new FD: {A,B,C} → E (Decomposed from FD1), CK: {A,B,C} {BC}+ = {BC} - Not a candidate key {ABC}+ = {ABCDE} - A candidate key {BCD}+ = {ABCDE} - A candidate key Candidate Keys = {ABC}, {BCD} The result of the decomposition consists of R1 and R2 %3D %3D %3D

Task 4: Consider the relation schema R(A, B, C, D, E) with the following FDs FD1: {A,B,C} → {D,E} FD2: {B,C,D} → {A,E} FD3: {C} → {D} a) Show that R is not in BCNF. Ans) X = {C} then X+ = {C, D} which is not R therefore X is not a superkey, so R is not in BCNF. b) Decompose R into a set of BCNF relations (describe the process step by step). Ans) FD3 violates BCNF. Decomposing R using FD3. R1(C,D) with FDs: FD3, CK: {C} R2(A,B,C,E) with new FD: {A,B,C} → E (Decomposed from FD1), CK: {A,B,C} {BC}+ = {BC} - Not a candidate key {ABC}+ = {ABCDE} - A candidate key {BCD}+ = {ABCDE} - A candidate key Candidate Keys = {ABC}, {BCD} The result of the decomposition consists of R1 and R2 %3D %3D %3D

Database System Concepts

7th Edition

ISBN:9780078022159

Author:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Publisher:Abraham Silberschatz Professor, Henry F. Korth, S. Sudarshan

Chapter1: Introduction

Section: Chapter Questions

Problem 1PE

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