Relational Database Management System - DBMS Short Questions and Answers

21 The set of attributes X ⊆ Schema (R) is a super key for relation schema R only if :

A For all relations r over R the number of tuples in projection over X of r is the same as the number of tuples in r

B All attributes of X are having non null values

C All attributes of X are having unique values

D None of the above

Answer: Option [C]

22 B+ Trees are preferred to binary trees since :

A Disk capacities are higher than memory capacities

B Memory access is faster than disk access

C Disk are more reliable than memory

D Disk data transfer rates are much less than memory transfer rates

Answer: Option [B]

23 The physical location of a record is determined by a mathematical formula that transforms a file key in to a record location in :

A AB-tree File

B An indexed file

C A hashed file

D None of the above

Answer: Option [C]

24 To represent many to many relationship between two entity types A and B in a relational model :

A put identifying attribute (s) of A in the relation representing B

B put identifying attribute (s) of B in the relation representing A

C create a new relation to represent the relationship

D it can not be represented

Answer: Option [B]

25 Which of the following is not a valid relational database ?

A SYBASE

B Oracle

C FoxPro

D UNIFY

Answer: Option [D]