Consider the ER diagram show below The relational reduction

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.

student PK student id stu ac Count name media account PK account id url Username

Solution

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.