Remove a table from your database diagram if you do not want it to appear in the diagram. Removing a table does not alter your server 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:
For example, suppose you add a table to your diagram so that you can copy its column definitions for address data to a new table you are creating. If you cut the column definitions in the existing table instead of copying them, that table would be marked as modified. In this case, you would discard your changes to that table before removing it. However, if you wanted to move those column definitions to your new table and then remove the existing table from your diagram, you would save your changes to the existing table before removing it.
To remove a table from a database diagram
-or-
Click the Remove Table from Diagram button 
on the Database Diagram toolbar.
If the table has unsaved changes as a result of edits made in the database diagram by you or another user, 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.
Note If you create a new table, then remove it from the diagram before saving it to the database, the table name remains in memory until you close the database diagram. Also, if you delete an existing table from the database, the table name remains in memory. To use the table name again, close and restart the Database Designer.