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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 ?
B Oracle
C FoxPro

Answer: Option [D]

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