When you create a relationship between two tables, you can set referential integrity.
Referential integrity can also prevent accidental deletion or editing of data.
When you set referential integrity, you must observe the following three rules. First, you cannot enter data in the join field in the related table that does not have a match in the join field in the primary table. Second, you cannot delete records from the primary table if there are matching records in the related table. Third, you cannot edit primary key values in the primary table if related records exist. However, if you want to perform the changes listed above and still maintain referential integrity, you can select the Cascade Update Related Fields and Cascade Delete Related Records options in the Edit Relationships dialog box.