UGC NET COMPUTER SCIENCE SOLVED PAPERS 2014-16 - UGC NET Computer Science Paper 3 August 2016

6. The output of the following combinational circuit

  • Option : D
  • Explanation :

    So, option (D) is correct.
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7. Which of the following statements is/are True regarding some advantages that an object-oriented DBMS (OODBMS) offers over a relational database?
I. An OODBMS avoids the “impedance mismatch” problem.
II. An OODBMS avoids the “phantom” problem.
III. An OODBMS provides higher performance concurrency control than most relational databases.
IV. An OODBMS provides faster access to individual data objects once they have been read from disk.

  • Option : B
  • Explanation :
  • An OODBMS avoids the “impedance mismatch” problem.Correct.
  • An OODBMS doesn't avoids the “phantom” problem.
  • An OODBMS doesn't provides higher performance concurrency control than most relational databases. Since it is distributed.
  • An OODBMS provides faster access to individual data objects once they have been read from disk.Correct
  • SO, option (B) is correct.
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8. The Global conceptual Schema in a distributed database contains information about global relations. The condition that all the data of the global relation must be mapped into the fragments, that is, it must not happen that a data item which belongs to a global relation does not belong to any fragment, is called:

  • Option : B
  • Explanation :
    The condition that all the data of the global relation must be mapped into the fragments, that is, it must not happen that a data item which belongs to a global relation does not belong to any fragment, is called Completeness condition. In distributed system it is convenient that fragment to be disjoint, so that the replication of data can be controlled explicitly at the allocation level.this is called Disjointness condition To reconstruct any global relation from its fragment is called Reconstruction condition. The formation of no. of fragments into a cluster is called Aggregation condition. So, option (B) is correct.
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9. Suppose database table T1(P, R) currently has tuples {(10, 5), (15, 8), (25, 6)} and table T2 (A, C) currently has {(10, 6), (25, 3), (10, 5)}. Consider the following three relational algebra queries RA1, RA2 and RA3:
RA1 : T1 ⨝ T1.P = T2.A T2 where ⨝is natural join symbol
RA2 : T1 ⟕ T1.P = T2.A T2 where ⟕ is left outer join symbol
RA3 : T1 ⨝ T1.P = T2.A and T1.R = T2.CT2 
The number of tuples in the resulting table of RA1, RA2 and RA3 are given by:

  • Option : D
  • Explanation :
    RA1 : T1 ⨝ T1.P = T2.A T2 where ⨝is natural join symbol. It will result 3 tuples:
    P = ARC
    1056
    1055
    2563
    RA2 : T1 ⟕ T1.P = T2.A T2 where ⟕ is left outer join symbol. It will result in 4 tuples.
    P = ARC
    1056
    1055
    158Null
    2563
    RA3 : T1 ⨝ T1.P = T2.A and T1.R = T2.CT2. It will result in 1 tuple.
    P = AR = C
    105
    So, option (D) is correct.
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10. Consider the table R with attributes A, B and C. The functional dependencies that hold on R are : A → B, C → AB. Which of the following statements is/are True ?
I. The decomposition of R into R1(C, A) and R2(A, B) is lossless.
II. The decomposition of R into R1(A, B) and R2(B, C) is lossy.

  • Option :
  • Explanation :
    Decomposition of R into R1(C, A) and R2(A, B) is lossless. Because C → A, A → B. So, C → AB can be derived and there is no loss. Decomposition of R into R1(A, B) and R2(B, C) is lossy. Because A → B, C → B are derived but we can't derive C → AB, So it is lossy. So, option (C) is correct.
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