11.6. Relationships

In Access, relationships are defined in the Relationships window, as shown in Figure 11-19. Defining relationships enables the database itself to enforce referential integrity. In brief, referential integrity can be explained as requiring that a record is established in the primary (parent) table before an entry can be created in the child table; typically the "many" side of a one-to-many relationship between tables. The value in the foreign key field of the child table must equal a value in the primary key field in the parent table; otherwise the database will not allow the record to be created in the child table.

When referential integrity is selected, there are two additional relationship options, CascadeUpdate Related Fields and CascadeDeleteRelated Records.Cascade update will update the related fields if the value in the parent field is changed, while cascade delete will delete the related record if the parent record is deleted.