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15 votes
15 votes

How many minimum relations required for given ER diagram ?

13 Answers

2 votes
2 votes

R4 Relationship is not given, therefore, if we want to have minimum no. of tables, we can consider R4 as either 1:1 or 1:N Relationship. 

  • Entities - we have 5 Entities (E1, E2, E3, E4 and E5 (weak entity)). For each Entity, we have a Relation (or, table). Therefore, 5 Tables are required.
  • Attributes - Since, we don't have any Multi-valued Attribute, we don't require any Relation (or, table).
  • Relationship - Except R1, R2 (Both are many to many Relationship. R2 is recursive relationship) and R5 (a Identifying Relationship), all the other Relations are either 1:1 or 1:N, therefore, we don't require Relation (or, table) for these Relationships. We require a Relation (or, table) for many to many Relationship. Hence, two Relations (or, table) as we have two many to many Relationship (i.e. R1 and R2).

Total = 5 + 0 + 2 = 7

edited by
1 votes
1 votes
5 for each entity set and 3 different tables for the relationships R1, R2 and R5 since they are many-to-many relationships.Thus, total 8.
0 votes
0 votes
7 tables

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How many minimum relations required for the above ER diagram?According to me it should be 7. Please let me know the answer according to you.