side of the relationship. For example, enforcing referential integrity between the two Employee # fields, tells Access not to accept an employee number in the Sale table that has not been defined in the Employee table. Enforcing referential integrity is a strong control, as it greatly limits the amount of data entry errors. When you enforce referential integrity, Access labels relationships with $1$ and $$ symbols. If you do not enforce referential integrity, Access does not label the relationships.

e$.$ Select Create and Access returns to the Relationship Window.

Establish the remaining relationships.

Data Entry

Once the tables have been defined and relationships have been established, the database is ready to begin storing information. The only trick to data entry is to remember the restrictions created when referential integrity is enforced. For example, data must be entered into the Customer and Employee tables before a record can be entered into the Sale table because the customer numbers and employee numbers entered in the Sale table must already exist in the Employee and Customer tables.