title: ORA-01722: invalid number for a simple query
body: <p>I noticed the same topics here but I just couldn't find the answer because of my noob skill in databases, I tried a couple of answers but didn't work, apologies. </p>
  
  <p>I have 5 tables and triggers for each of them if the user INSERT, UPDATE, DELETE</p>
  
  <p>After I inserted the data into <code>TRAFFIC, (date (varchar30), input_quant (varchar30), output_quant (varchar30), status (varchar30) )</code></p>
  
  <p>I've tried a simple query</p>
  
  <pre><code>select sum (input_quant)status from traffic;
  </code></pre>
  
  <p>But the error pops out:</p>
  
  <pre><code>ORA-01722: invalid number
  01722. 00000 -  "invalid number"
  *Cause:    
  *Action:
  </code></pre>
  
  <p>Is it because of the type (<code>VARCHAR</code>)?</p>
  
  <p>In the table TRAFFIC and SUPPLY I had to DISABLE the FKs so that I can insert the data, but now that I have inserted them, I can't ENABLE them (parent key not found). I don't think this has something to do with "INVALID NUMBER" error. But I'm still confused. What should I do? </p>