In a database diagram, you cannot undo actions once they have been completed. However, you can cancel an action before it is completed.
The following table lists actions and how you can cancel them before they are completed.
| Type of action | To cancel the action |
| Dragging a table into a database diagram | Before you release the mouse button, drag-and-drop the objects outside the diagram or press the ESC key. |
| Typing in a table cell | Press the ESC key before exiting the cell. |
| Editing a property inside the properties pages dialog box | Press the ESC key before exiting the field. |
| Creating a relationship line | Before you release the mouse button, drag the line to the diagram background. –or– Choose Cancel in the Create Relationship Dialog Box. |
Even though you cannot undo a deletion, you can make sure that the deletion does not take effect in your database by closing the affected diagrams without saving them first.
If you want to save some of the tables in your diagram but not others, select them and choose Save Selection from the File menu. Then close the diagram; the unsaved changes will be discarded.