Project ForgeConsider an ER diagram: entity M (attributes M1 (key), M2, M3) connects via a regular relationship R1 (with an arrow pointing from R1 into P, indicating many M's per one P) to entity P (attributes P1 (key), P2), which connects via an identifying relationship R2 (double diamond, arrow into P) to a WEAK entity N (double rectangle, attributes N1 (partial key, dashed underline), N2). The minimum number of tables needed to represent M, N, P, R1, R2 is
- A2
- 3
- C4
- D5
Explanation
P is a strong entity: 1 table {P1,P2}. R1 is a regular many-to-one relationship (M side is 'many'), so it merges into M's table as a foreign key referencing P: 1 table {M1,M2,M3,P1}. N is a weak entity with identifying relationship R2 — by standard ER-to-relational mapping rules, a weak entity and its identifying relationship merge into ONE table combining N's own attributes with a foreign key to its owner P: 1 table {N1,N2,P1}. Total: 3 tables.
Source: GATE CS 2008 (2008)
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