7.3

Explain how functional dependencies can be used to indicate the following:

• A one-to-one relationship set exists between entity sets student and instructor.
• A many-to-one relationship set exists between entity sets student and instructor.

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Let $Pk(r)$ denote the primary key of relation $r$.

• The functional dependencies $Pk(student)\to Pk(instructor)$ and $Pk(instructor)\to Pk(student)$ indicate a one-to-one relationship because any two tuples with the same value for student must have the same value for instructor, and any two tuples agreeing on instructor must have the same value for student.

• The functional dependency $Pk(student)\to Pk(instructor)$ indicates a many-to-one relationship since any student value which is repeated will have the same instructor value, but many student values may have the same instructor value.