16.Consider a relation R = (A,B,C,D,E) with the following functional dependencies: {C,E → D, D → B, C → A} and identify a candidate key. None of them {C,E,D} {C,E,B} {C,E} 17.A join in which tuples from R1 that do not have matching values in the common attributes of R2 are also included in the result relation. R1 left outer join R2 R1 semi join R R1 equi join R2 R1 natural join R2 18.When two transactions that access the same database items have their operations interleaved in a way that makes the values of some database items incorrect this problem is call? none of them dirty read summary problem the lost update problem 19.Protect the database from inconsistencies and data loss Database recovery Database Transaction & Concurrency control Concurrency control Concurrency control & Database recovery 20.Let E1 and E2 be two entity types in an entity relationship diagram. E1 have all three simple single-valued attributes while E2 have two simple single-valued attributes and two simple multi-valued attributes. R1 and R2 are two relationships between E1 and E2, where R1 is one-to-many and R2 is many-to-many. RI and R2 do not have any attributes of their own. What is the minimum number of tables required to represent this situation in the relational model? a)3 b)2 c)4 d)5

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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DATABASE SYSTEMS

16.Consider a relation R = (A,B,C,D,E) with the following functional dependencies:

{C,E → D, D → B, C → A} and identify a candidate key.

None of them
{C,E,D}
{C,E,B}
{C,E}

17.A join in which tuples from R1 that do not have matching values in the common attributes of R2 are also included in the result relation.

R1 left outer join R2
R1 semi join R
R1 equi join R2
R1 natural join R2

18.When two transactions that access the same database items have their operations interleaved in a way that makes the values of some database items incorrect this problem is call?

none of them
dirty read
summary problem
the lost update problem

19.Protect the database from inconsistencies and data loss

Database recovery
Database Transaction & Concurrency control
Concurrency control
Concurrency control & Database recovery

20.Let E1 and E2 be two entity types in an entity relationship diagram. E1 have all three simple single-valued attributes while E2 have two simple single-valued attributes and two simple multi-valued attributes. R1 and R2 are two relationships between E1 and E2, where R1 is one-to-many and R2 is many-to-many. RI and R2 do not have any attributes of their own. What is the minimum number of tables required to represent this situation in the relational model?

a)3

b)2

c)4

d)5

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