Let A and B be two entities in an E-R diagram, each having only simple…
2025
Let A and B be two entities in an E-R diagram, each having only simple single-valued attributes. R1 and R2 are two relationships between A and B. R1 is one-to-many from A to B, and R2 is many-to-many from A to B. What is the minimum number of tables required to represent A, B, R1 and R2 in the relational model?
- A.
4
- B.
2
- C.
6
- D.
3
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Correct answer: D
Key idea: Entity tables and relationship tables are counted differently during ER-to-relational mapping.
Entity A requires one table.
Entity B requires one table.
R1 is one-to-many, so it can be represented using a foreign key on the many side; no separate table is required.
R2 is many-to-many, so it requires one separate junction table.
Total: 1 (A) + 1 (B) + 1 (R2 junction table) = 3 tables.
Final answer: 3.