Participation Constraint:

Determines whether the existence of an entity depends on its being related to another entity through the relationship.

i. Total Participation:

• The participation is total if an entiy’s existence requires the existence of an associated entity in a particular relationship.

• Example

  An employee MUST work for a department.

  An employee entity can exist only if it participates in a WORKS_FOR relationship instance

  Thus its participation is TOTAL

ii. Partial Participation:

• The participation is partial for the vice versa.

• Example

  Only some employees manage departments

  The participation is PARTIAL.

A formal constraint: (m, n) where m, n are number of times

• Constraint:(min, max) where m, n are min and max number of times an entity participates in a relationship instance.
• For example, (0,10) means partial participation, and (1,max) means total participation.
• Some instances of the WORK_FOR relationship:
• ln relationship set, it is natural to expect that each employee works in at least one department and that each department has at least one employee.
• This means that the participation of both Employees and Departments in WORKS_FOR is total.
• But now only some employees can manage department not all. This means that the participation of both Employees and Departments in WORKS_FOR is partial.