Unformatted text preview: of the optional entity. The corresponding minimal cardinality is 0. Mandatory participation: means that one entity occurrence requires a corresponding entity recurrence in a particular relationship. If no optionality symbol is depicted, the relationship is assumed to be mandatory. The existence of a mandatory participation implies a connectivity of 1 and a minimum cardinality of 1. Relationship degrees: A relationship degree indicates the number of entities or participants associated with the relationship. A unary relationship exists when an association is maintained within a single entity. For example: an employee within the EMPLOYEE entity is the manager of one or more employees within the entity. In this case, the "manages" relationship means that EMPLOYEE requires that another EMPLOYEE be the manager that is EMPLOYEE has a relationship with itself . This is known as a recursive relationship. Recursive relationships are represented like: manages EMPLOYEE A binary relationship requires two entities to be related. These are the most common type...
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This document was uploaded on 03/07/2014.
- Spring '09