Consider the E-R diagram show below – The relational reduction results in three

Question

Consider the E-R diagram show below –

The relational reduction results in three relations, one each for the entity sets and one for the relationship set. The relationship set relation is

stu_account(student_id, account_id)

All attributes of the student_account relation are constrained to be not null. Based on the E-R diagram, which attribute(s) or combination of attributes should be constrained to be unique? Use the response format described in the preceding note.

Explanation / Answer

If each student has one account id then

student_id can be unique. or

(student_id,account_id) also can be considered to be unique key.

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