title: Minus operator returns error ora-01722
body: <p>I have <strong>row</strong>, which is a character field, but is compared to numeric values in conditions. This causes ORA-01722 invalid number error under some circumstances.</p>
  
  <p>Instead of: <strong>row</strong> in (1, 2, 3, 4, 5, 7)</p>
  
  <p>It should be:   <strong>row</strong> in (‘1’, ‘2’, ‘3’, ‘4’, ‘5’, ‘7’)</p>
  
  <p>This query returns ORA-01722:</p>
  
  <pre><code>(select * from table@production)
  minus
  (select * from table)
  </code></pre>
  
  <p>How can the query above be modified?</p>