title: SQL join table with 12 column composite PK with itself painlessly
body: <p>I have a table with a composite natural primary key that involves 12 columns (c1, c2, ..., c12).</p>
  
  <p>I want to write a self join query:</p>
  
  <pre><code>SELECT *
  FROM T1 AS a
  JOIN T1 AS b ON a.c1 = b.c1 AND a.c2 = b.c2 AND ... AND a.c12 = b.c12;
  </code></pre>
  
  <p>This join is a pain to write. Is there a better way?</p>