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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

Comment

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

Comment

Answer: Option [B]

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(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

Comment

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

Comment

Answer: Option [B]
(25) Which of the following is not a valid relational database ?
[A] SYBASE
[B] Oracle
[C] FoxPro
[D] UNIFY

Comment

Answer: Option [D]

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