How to: Change Relationship Properties (Visual Database Tools)
Referential integrity between tables is enforced by default when you create a relationship. An enforced relationship ensures each value entered in a foreign key column matches an existing value in the related primary key column.
You can change the conditions under which referential integrity is enforced by editing the relationship's properties.
To change relationship properties
In Object Explorer, right-click the table involved in the relationship, and click Modify.
The table opens in Table Designer.
From the Table Designer menu, click Relationships.
In the Foreign Key Relationships dialog box, select the relationship in the Selected Relationship list.
Change properties for the relationship in the grid.
The relationship is updated in the database when you save the table.