Question

Which of the following statements is not correct?

(a) The primary key must be unique for a given table

(b) Specifying a zero (0) for the lower bound for the association multiplicity on a class diagram indicates that the item is required

(c) Specifying a one (1) for the lower bound for the association multiplicity on a class diagram indicates that the item is required

(d) Most databases allow multiple records that are identical

I got this question during a job interview.

This key question is from Foreign, Candidate, Primary, Composite, Unique Keys topic in portion Planning Oracle Applications of Oracle

Answer 1

Correct choice is (b) Specifying a zero (0) for the lower bound for the association multiplicity on a class diagram indicates that the item is required

Easy explanation: A foreign key is a column that references a column (most often the primary key) of another table. The purpose of the foreign key is to ensure referential integrity of the data. In other words, only values that are supposed to appear in the database are permitted.