Consider the following ER diagram. Question: Which of the following is a…

2008

Consider the following ER diagram.

ER diagram with entities M, P, weak entity N, and relationships R1 and R2

Question: Which of the following is a correct attribute set for one of the tables in the minimum relational schema for M, N, P, R1, and R2?

Answer: A. M1, M2, M3, P1 — Minimum number of tables: 3. M table: M(M1, M2, M3, P1). Relationship R1 can be represented by adding P1 as a foreign key in M. P table: P(P1, P2). N table:…

  1. A.

    M1, M2, M3, P1

  2. B.

    M1, P1, N1, N2

  3. C.

    M1, P1, N1

  4. D.

    M1, P1

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Show answer & explanation

Correct answer: A

Minimum number of tables: 3.

  • M table: M(M1, M2, M3, P1). Relationship R1 can be represented by adding P1 as a foreign key in M.

  • P table: P(P1, P2).

  • N table: N(P1, N1, N2). N is a weak entity identified through P, so P1 is included with N1 and N2; commonly (P1, N1) forms the key.

So the student concern is partly valid: N1 and N2 are included in the N table. However, among the listed options, the only complete attribute set that matches one of the minimum-schema tables is M1, M2, M3, P1.

Correct answer: M1, M2, M3, P1.

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