title: Insert a Row Only if a Row does not Exist
body: <p>I am building a hit counter. I have an article directory and tracking unique visitors. When a visitor comes i insert the article id and their IP address in the database. First I check to see if the ip exists for the article id, if the ip does not exist I make the insert. This is two queries  -- is there a way to make this one query</p>
  
  <p>Also, I am not using stored procedures I am using regular inline sql</p>