###### Database-Management-System

October 10, 2023###### UGC NET CS 2018 DEC Paper-1

October 10, 2023# Database-Management-System

Question 40 |

Consider a schema R(A,B,C,D) and functional dependencies A → B and C → D. Then the decomposition of R into R_{1}(AB) and R_{2}(CD) is

dependency preserving and lossless join | |

lossless join but not dependency preserving | |

dependency preserving but not lossless join | |

not dependency preserving and not lossless join |

Question 40 Explanation:

If the given relations are to be lossless then

R

Given R

R

Not lossless.

The given relation decomposed into R

R

_{1}∩R_{2}≠ 0Given R

_{1}(A,B), R_{2}R

_{1}∩R_{2}= 0Not lossless.

The given relation decomposed into R

_{1}(A,B) and R_{2}(C,D) and there are only two functional dependencies A→B and C→D. So the given decomposition is dependency preserving.Correct Answer: C

Question 40 Explanation:

If the given relations are to be lossless then

R

Given R

R

Not lossless.

The given relation decomposed into R

R

_{1}∩R_{2}≠ 0Given R

_{1}(A,B), R_{2}R

_{1}∩R_{2}= 0Not lossless.

The given relation decomposed into R

_{1}(A,B) and R_{2}(C,D) and there are only two functional dependencies A→B and C→D. So the given decomposition is dependency preserving. Subscribe

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