Let E₁ and E₂ be two entities in an E/R diagram with simple single-valued…
2005
Let E₁ and E₂ be two entities in an E/R diagram with simple single-valued attributes.
R₁ and R₂ are two relationships between E₁ and E₂, where R₁ is one-to-many and R₂ is many-to-many.
R₁ and R₂ do not have any attributes of their own.
What is the minimum number of tables required to represent this situation in the relational model?
- A.
2
- B.
3
- C.
4
- D.
5
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Correct answer: B
To represent the E/R diagram in the relational model:
1. Each entity with simple attributes is represented by a table. So E₁ and E₂ each become one table.
2. A one-to-many relationship (R₁) is represented by adding a foreign key to the table on the 'many' side. No separate table is needed.
3. A many-to-many relationship (R₂) requires a separate junction table to store the pairs of primary keys from E₁ and E₂.
4. Total tables: 2 (for E₁ and E₂) + 1 (for R₂) = 3.
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