title: How can we calculate the number of days between two dates in oracle-sql ? exact syntax?
body: <p>I have tried this</p>
  
  <pre><code>select datediff(day,doi,dateeg) from Cardholders;
  </code></pre>
  
  <p>error:ORA-00904 : "DATEDIFF" invalid identifier</p>
  
  <p>here doi and dateeg are of date datatype in cardholders relation ?</p>