GATE | GATE CS 2008 | Question 85
Consider the following ER diagram.
The minimum number of tables needed to represent M, N, P, R1, R2 is
Explanation: Answer is B, i.e, 3 minimum tables.
M, P are strong entities hence they must be represented by separate tables.
Many-to-one and one-to-many relationship sets that are total on the many-side can be represented by adding an extra attribute to the “many” side, containing the primary key of the “one” side. ( This way no extra table will be needed for Relationship sets )
M table is modified to include primary key of P side(i.e. P1). N is weak entity, and is modified to include primary key of P (i.e, P1).
Therefore there would be minimum of 3 tables with schema given below :
M ( M1, M2, M3, P1) P ( P1, P2 ) N ( P1, N1, N2 )
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