title: How to update a serial number in oracle table based on time of entry of the record in the same table
body: <p>I have a table named entryform having the following columns
  <code>NAME,BOOKING_TIME,SN</code>
  The NAME and BOOKING_TIME fields are entered by the users. The SN field is to be updated based on the ascending sequence of BOOKING_TIME.</p>
  <p>Can some please help me out to write the SQL query for performing the above operation in ORACLE</p>