title: What are Oracle hidden fields?
body: <p><a href="http://download.oracle.com/docs/cd/B13789_01/server.101/b10755/statviews_1179.htm" rel="noreferrer">ALL_TAB_COLS</a> differs from <a href="http://download.oracle.com/docs/cd/B13789_01/server.101/b10755/statviews_1180.htm#I1020277" rel="noreferrer">ALL_TAB_COLUMNS</a> in that hidden columns are not filtered out.</p>
  
  <p>What are hidden fields?</p>
  
  <blockquote>
    <p>This view differs from "ALL_TAB_COLUMNS" in that hidden columns are
    not filtered out.</p>
  </blockquote>