Developers can add a table to their database diagram to edit its structure or relate it to other tables in their diagram.. When Developers working with SQL Server “Denali”, MS SQL Server 2008 R2 and MS SQL Server 2005 want to add related tables to a diagram, they should follow the next steps:
1. Add the table with relationships to a database diagram.
2. Right-click the table and from the shortcut menu and click Add Related Tables.