title: MINUS two Tables based on 2 columns
body: <blockquote>
    <p>I need to SELECT the rows of
    <strong>'billing_temp'</strong> that
    <strong>doesn't exist in 'billing'</strong> based on
    two columns.</p>
  </blockquote>
  
  <p>Currently I come-up with this query:</p>
  
  <pre><code>SELECT ControlNum, CarrierName, PhoneNum, PatientName, SubscriberID, SubscriberName, 
  ChartNum, DoB, SubscriberEmp, VisitID, ServiceDate, ProviderName, CPTCode, BillingDate, 
  AgingDate, BalanceAmt, Age, AgeCategory FROM billing_temp LEFT JOIN billing 
  USING (ControlNum, CPTCode) WHERE billing.ControlNum=billing_temp.ControlNum AND 
  billing.CPTCode=billing_temp.CPTCode
  </code></pre>
  
  <p>But I'm getting the error:</p>
  
  <pre><code>Column 'ControlNum' in fieldlist is ambiguous.
  </code></pre>
  
  <p>Does anyone faced this occurrence.</p>
  
  <p>If you need further details to recover this, inform me..
  Help me. Thanx in advance..</p>
  
  <p><strong>NOTE :</strong> </p>
  
  <p>I'm so sorry that I've found what is the problem in my own query.. 
  Thanks for all who paid interest in my question and sent the answer..</p>