You can copy a table from one database diagram to another in the same database.
Copying a table from one database diagram to another diagram merely adds a reference to the table in the second diagram. The table is not duplicated in your database. For example, if you copy the authors
table from one database diagram to another, each diagram references the same authors
table in the database.
To copy a table from another database diagram
When you edit the table in either diagram, your changes are reflected in both diagrams. Similarly, once you save the table in either diagram, the table is no longer considered "modified" in either diagram. For more information, see Interactions Among Table Diagrams and Table Designer Windows.
Adding Tables to a Database Diagram | Database Designer | Duplicating a Table | Tables