title: Oracle equivalent of NVL for number datatype
body: <p>What is the Oracle equivalent of NVL for number datatypes?</p>
  
  <p>This works since the datatype is VARCHAR:</p>
  
  <pre>    select nvl(enrol.OUAC_APPLNO, 'blank') Invalid_OUAC_APPLNO</pre>
  
  <p>But this doesn't work since the datatype is NUMBER:</p>
  
  <pre>    select nvl(enrol.ouac_type_id, 'blank') REGTYP</pre>