title: ORA-017779 : cannot modify a column which maps to non key-preserved table
body: <p>How can I solve this error:</p>
  
  <blockquote>
    <p>ORA-017779 : cannot modify a column which maps to non key-preserved table.</p>
  </blockquote>
  
  <p>My Code:</p>
  
  <pre><code>UPDATE   (SELECT SOBS034.T1 as OLD, SOBS063.T1 as NEW
            FROM SOBS034 
            INNER JOIN SOBS063  ON SOBS034.ID = SOBS063.ID
            where  SOBS034.ID='111000' AND SOBS063.T2='' ) t
  SET t.OLD =t.NEW 
  </code></pre>