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RELATIONAL STRUCTURES FOR UNARY AND TERNARY RELATIONSHIPS
Unary One-to-Many Relationships
Let's continue with the General Hardware Co. example of Figure 5.14, reprinted
here for convenience as Figure 6.1. Suppose that General Hardware's salespersons
are organized in such a way that some of the salespersons,
in addition to
having
their customer responsibilities, serve as the sales managers of other salespersons,
Figure 6.2. A salesperson reports to exactly one sales manager, but each salesperson
who serves as a sales manager typically has several salespersons reporting to
him. Thus, there is a one-to-many relationship within the set or entity type of
salespersons.
Salesperson who is also a sales manager
Salesperson
This is known as a unary one-to-many relationship. It is unary because there is
only one entity type involved. It is one-to-many because among the individual
entity occurrences, i.e. among the salespersons, a particular salesperson reports
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