Delete a table from your database when you want to do all of the following:
A table that is marked for deletion is permanently deleted from the database when you save your database diagram. A reference to that table continues to exist in memory until you save the database diagram. If you close the database diagram without saving it, the table will continue to exist in your database and appear in your database diagram and every other database diagram in which it appeared before you marked it for deletion.
Note Deleting a table automatically removes any relationships to it.