Database miscellaneous
- Consider an Entity-Relationship(ER) model in which entity sets E1 and E2 are connected by an m : n relationship R12. E1 and E3 are connected by a 1 : n (1 on the side of E1 and n on the side of E3) relationship R13. E1 has two single-valued attributes a11 and a12 of which a11 is the key attribute. E2 has two single-valued attributes a21 and a22 of which is the key attribute. E3 has two singlevalued attributes a31 and a32 of which a31 is the key attribute. The relationships do not have any attributes. If a relational model is the derived from the above ER model, then the minimum number of relations that would be generated if all the relations are in 3NF is _______.
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E1 (a11, a12), E2 (a21, a22), E3 and R13 (a11, a31, a32), R2 (a11 , a12), But in table (a11, a31, a32) there may be transitive dependency between a11 and a32 so we should decompose this table into 2 more tables.Correct Option: B
E1 (a11, a12), E2 (a21, a22), E3 and R13 (a11, a31, a32), R2 (a11 , a12), But in table (a11, a31, a32) there may be transitive dependency between a11 and a32 so we should decompose this table into 2 more tables.
- An ER model of a database consists of entity types A and B. These are connected by a relationship R which does not have its own attribute. Under which one of the following conditions, can the relational table for R be merged with that of A?
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In one to many or many to one participation, relation is merged in table which is on many side and if there participation then relation is merged in that side consider entity set A, B in the relationship set R. Relation R merge with that of A and B.
According to the above figure. Many to one relationship set can merge towards entity set 'A' & Participation towards A side can be total. Hence option (c) is correct.Correct Option: C
In one to many or many to one participation, relation is merged in table which is on many side and if there participation then relation is merged in that side consider entity set A, B in the relationship set R. Relation R merge with that of A and B.
According to the above figure. Many to one relationship set can merge towards entity set 'A' & Participation towards A side can be total. Hence option (c) is correct.
