title: insert record if not exists in sql, duplicate column name
body: <p>i wanted a solution to insert a record if it isn't there so i searched here and found a solution but i have another problem </p>
  
  <pre><code>INSERT INTO closed_answers (question_id, subject_id)
  SELECT * FROM (SELECT 2, 2) AS tmp
  WHERE NOT EXISTS (
      SELECT question_id FROM closed_answers WHERE question_id = 2 AND subject_id = 2
  ) LIMIT 1
  </code></pre>
  
  <p>the output is</p>
  
  <pre><code>#1060 - Duplicate column name '2'
  </code></pre>
  
  <p>if i used any 2 numbers that aren't identical it will work but the problem arise when the 2 numbers are the same</p>