Tables and Columns Dialog Box (Visual Database Tools)
Use this dialog box to map a primary key in one table to a foreign key in another. To access this dialog box, from the Table Designer menu, click Relationships. In the Foreign Key Relationships dialog box, click the Tables and Columns Specification field, and then click the ellipses (…) to the right of the property.
If the table is published for replication, you must make schema changes using the Transact-SQL statement ALTER TABLE or SQL Server Management Objects (SMO). When schema changes are made using the Table Designer or the Database Diagram Designer, it attempts to drop and recreate the table. You cannot drop published objects, therefore the schema change will fail.
The columns you choose for the foreign key must have the same data type of the primary columns they correspond to. There must be an equal number of columns in each of the keys. For example, if the primary key of the table on the primary side of the relationship is made up of two columns, you will need to match each of those columns with a column in the table for the foreign key side of the relationship.