You can remove a table from your database diagram. Removing a table does not alter your database. The table and its relationships to other tables continue to exist in the database.
If you remove a table that has been changed either by you or another user, a message prompts you to save the table before removing it:
To remove a table from a database diagram
If the table has unsaved changes as a result of edits you made in the database diagram, a message prompts you to save the table before removing it.
The table is removed from your diagram but it continues to exist in the database.
Database Designer | Deleting a Table from a Database Diagram and the Database | Tables