A primary key or unique constraint must be defined for table <Tablename> before it can participate in a relationship. (Visual Database Tools)

In order to create a foreign key relationship, at least one of the two tables must have a primary key or unique constraint defined. To create the relationship you are attempting to create, first create a primary key for one of the tables.

See Also

Concepts

Error Messages in Visual Database Tools

Help and Information

Getting SQL Server 2005 Assistance