If you delete the last row on a data page, the page is deallocated and the next and previous page pointers on the adjacent pages are changed.
The rows that point to that page in the leaf and intermediate levels of the index are removed.
If the deallocated data page is on the same extent as other pages belonging to the table, it can be used again when that table needs an additional page.
If the deallocated data page is the last page on the extent that belongs to the table, the extent is also deallocated and becomes available for the expansion of other objects in the database.
In Figure 9-6, which shows the table after the deletion, the pointer to the deleted page has been removed from index page 1007 and the following index rows on the page have been moved up to keep the used space contiguous.
Figure 9-6: Deleting the last row on a page (after the delete)