title: Why are these NVL() statements wrong in SQL?
body: <pre><code>SELECT inv_no,NVL2(inv_amt,inv_date,'Not Available')
  FROM invoice;
  
  SELECT inv_no,NVL2(inv_amt,inv_amt*.25,'Not Available') FROM invoice;
  </code></pre>
  
  <p>getting</p>
  
  <pre><code>ORA-01858: a non-numeric character was found where a numeric was expected
  ORA-01722: invalid number
  </code></pre>
  
  <p>respectively
  Please suggest what are the datatypes I can give in expr1 and expr2.</p>
  
  <p>Also Please tell me how this is right?</p>
  
  <pre><code>SELECT inv_no,NVL2(inv_date,sysdate-inv_date,sysdate)
  FROM invoice
  </code></pre>