title: SQL - Only select row that is not duplicated
body: <p>I need to transfer data from one table to another. The second table got a primary key constraint (and the first one have no constraint). They have the same structure. What I want is to select all rows from table A and insert it in table B without the duplicate row (if a row is0 duplicate, I only want to take the first one I found)</p>
  
  <p>Example :</p>
  
  <pre><code>MyField1 (PK)   |   MyField2 (PK)   |   MyField3(PK)   |   MyField4   |   MyField5  
  
  ----------
  
  1               |   'Test'          |   'A1'           |   'Data1'    |   'Data1'  
  2               |   'Test1'         |   'A2'           |   'Data2'    |   'Data2'  
  2               |   'Test1'         |   'A2'           |   'Data3'    |   'Data3'  
  4               |   'Test2'         |   'A3'           |   'Data4'    |   'Data4'
  </code></pre>
  
  <p>Like you can see, the second and third line got the same pk key, but different data in MyField4 and MyField5. So, in this example, I would like to have the first, second, and fourth row. Not the third one because it's a duplication of the second (even if MyField4 and MyField5 contain different data).</p>
  
  <p>How can I do that with one single select ?</p>
  
  <p>thx</p>