INTERESTING QUESTION ON ER DIAGRAMS

Question

How many minimum number of tables are required for this ER Diagram?

Comments

i think 6 tables are required.?

Answer 1

3 for entities, 1 for multivalued attribute with E1 and 4 for four many to many(M-N) relationships.

Total = 8

Comments

Total 8 tables will be required.... 3 for the entities..... 1 for the multivalued attribute of E1....And 4 relation tables for many to many relations...... Hence total 3+1+4=8....

Answer 2

4 Tables are required at minimum

Reason:

R₃ can merge with E₂

E₂R₃ can merge with R₁

R₁E₂R₃ cannot merge with E₁, Hence separate table is required for R₁E₂R₃

Now R₄ cannot merge with E₃, Hence separate table is required for R₄

E₃ can merge with R₂

E₃R₂ can merge with E₁, Hence separate table is required for E₃R₂

E₁ has a multivalued attribute, Hence separate table is required for it.

 

         

Comments

why is R3 merged with E2 while R4 cant with E3 ?

Answer 3

Each M:N relation requires separate table. So 4 tables for each relation.

Each multivalued attribute requires one table. So 1 table for the only one multivalued attribute of E1.

Last, 3 tables for three entities for E1 E2 and E3. So total 8 tables.