title: Error: Unknown duplicates value on record with id
body: <p>I'm trying to <code>Upsert</code> the data to Account object using an external tool, Everything works fine but <code>Salesforce</code> is throwing error for few records when <code>upserting</code>.</p>
  
  <p>I was doing the upsertion process using the external id field. Except external id field no other field is having a unique constraint.</p>
  
  <p>I'm getting the following error -</p>
  
  <blockquote>
    <p>SF_ERROR: DUPLICATE_VALUE</p>
    
    <p>OBJ: Account - duplicate value found: unknown duplicates value on record with id: 001***********</p>
  </blockquote>
  
  <p>Please help me to solve the issue.</p>