Question

Consider the following entity relationship diagram (ERD), where two entities E1 and E2 have a relation R of cardinality 1 : m



The attributes of E1 and A11, A12 and A13 where A11 is the key attribute. The attributes of E2 are A21, A22 and A23 where A21 is the key attribute and A23 is a multi-valued attribute.
Relation R does not have any attribute. A relational database containing minimum number of tables with each table satisfying the requirements of the third normal form (3NF) is designed from the above ERD. The number of tables in the database is

• A. 2
• B. 4
• C. 3
• D. 5

Answer 1

The correct option is C 3

Given information is:


Relation table R combine with entity E2 (since 1-many relation. Relation combine with many side, in case of partial participation).
E1 (A11, A12, A13) with key A11
RE2 (A21, A22, A23, A11) with A21, A23
In RE2 partial dependence A21 $\to$ A22, A11 present: So, not in 2NF. To remove it we need 2 separate table i.e.
E1 (A11, A12, A13) with key A11
RE11 (A21, A23) with key A21, A23
RE22 (A21, A22, A11) with key A21
All the three tables are now in 3NF form.