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 are 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) 3
(C) 5
(D) 4
Answer: (B)
Explanation: Step 1: 1NF
T1: A11, A12, A13
T2: A11, A21, A22, A23 //because A23 is multivalued ,it has to be included in Key attribute
Step 2: 2NF // A23 is Multivalued attribute and not allowed in 2NF therefore new tables are:
T1: A11, A12, A13
T2: A11, A21, A22
T3: A21, A23
Step 3: 3NF // There is no transitive functional dependency in all tables , So in 3NF
Therefore answer is B
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