title: SQL INSERT Violation Primary Keys
body: <p>I have a table with a primary key composed of three columns: <code>CODE_TARIF, UNITE, MODE_LIV</code>. In my table there are three records with <code>MODE_LIV = 2</code>. Then I insert a record with <code>MODE_LIV = 4</code>.</p>
  
  <pre><code>INSERT INTO T_TARIF (
      CODE_TARIF, ZONE, UNITE, MODE_LIV, LIBELLE, TR_DEBUT, TR_FIN, MONTANT
  ) 
  SELECT 'Livr_A_50_99', '2', '1', '4', 'sdg', '50', '99', '90' 
  UNION ALL 
  SELECT 'Livr_A_50_99', '2', '1', '4', 'sdg', '50', '99', '90' 
  UNION ALL 
  SELECT 'Livr_A_50_99', '2', '1', '4', 'sdg', '50', '99', '90'
  </code></pre>
  
  <p>It returns an error (violation of primary key), which doesn't make any sense because <code>MODE_LIV = 2</code> is not equal to <code>MODE_LIV = 4</code>.</p>
  
  <p>I know I could add a surrogate key as an auto-incrementing identity column, but in my situation that isn't an option.</p>