title: DELETE FROM <subquery>
body: <pre><code>DELETE FROM (SELECT * FROM orders1 o,order_item1 i
  WHERE i.order_id = o.order_id );
  </code></pre>
  
  <p>above query has not mentioned particular  to delete rows.Instead of  i have mentioned a sub query.
  But this query executes without any error and deletes <code>order_item1</code> table rows.</p>
  
  <p>How oracle server decide which table rows should be deleted?
  why <code>orders1</code> table rows cannot be deleted?</p>