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Decomposition is Lossless or dependency preserving(in Hindi)
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In this lesson Nisha Mittal will provide solutions of questions of NTA NET computer science

Nisha Mittal is teaching live on Unacademy Plus

Nisha Mittal
🌟 MCA Gold Medalist 🌟 Star Educator 🌟Gate Qualified 🔴UGC NET qualified🔴🌟YouTuber ☆🌟BOOK published on LINUX ADMINISTRATION by kalyani publish

U
Unacademy user
very nice Ma'am. the hard work is visible in ur lessons. thank you very much
ma'am please provide some more question of dependency preservation
mam when a relation is lossy?
done madam.. thank you for the revision
  1. 12. Consider a schema R(A, B, C, D) and following functional dependencies B-> C C-D Then decomposition of R into R1 (A, B), R2 (B, C) and R3 (B, D) is (1) Dependency preserving and lossless join. (2) Lossless join but not dependency preserving. (3) Dependency preserving but not lossless join (4) Not dependency preserving and not lossless jo R(A,B,C,D) R1 (A, B) | R2 (B, C) | R3 (B, D) C -B B-D


  2. 12. Consider a schema R(A, B, C, D) and following functional dependencies B-> C C-D Then decomposition of R into R1 (A, B), R2 (B, C) and R3 (B, D) is (1) Dependency preserving and lossless join. (2) Lossless join but not dependency preserving. (3) Dependency preserving but not lossless join (4) Not dependency preserving and not lossless jo R(A,B,C,D) R1 (A, B) R2 (B, C) R3 (B, D) Note : C-> D is also preserved with following two C-> B and B-> D.


  3. 12. Consider a schema R(A, B, C, D) and following functional dependencies. A -> B B-> C C-> D D- B Then decomposition of R into R1 (A, B), R2 (B, C) and R3 (B, D) is (1) Dependency preserving and lossless join. (2) Lossless join but not dependency preserving. (3) Dependency preserving but not lossless join. (4) Not dependency preserving and not lossless join. R1n R2 B which is a primary key of R2 R2 n R3 B which is a primary key of both R2 and R3 R1 n R3 B which is a primary key of R3 R1 U R2 U R3 ( A, B,C,D So, above relation is lossless All the dependencies are preserved after the decomposition. So, above decomposition is also dependency preserving. Correct option is (a)


  4. 12. Consider a schema R(A, B, C, D) and following functional dependencies. A > B C D 1)DEPENDENCY PRESERVING AND LOSSLESS JOIN. Rin R2- B which is a primary key of R2 R2 n R3 B which is a primary key of both R2 and R3 R1 n R3 B which is a primary key of R3 R1 U R2 U R3 ( A, B,C,D So, above relation is lossless All the dependencies are preserved after the decomposition. So, above decomposition is also dependency preserving. Correct option is (a)


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