title: Inserting new rows in table if already not exisitng
body: <p>I have a table than over time can get bigger and I want to insert some of its rows in another table but I also want to make sure I am not duplicating the rows that I had inserted before.
  So here is the type of condition for my <code>insert</code>:</p>
  
  <pre><code>INSERT INTO SecondTable(Col1,Col2)
  SELECT Col5,Col6
  FROM
  FirstTable ft
  WHERE ft.RecType = 'ABC'
  </code></pre>
  
  <p>So if I keep running this it will keep inserting the same rows again and again. How can I tell it only insert if it is not already there? </p>