title: What is a Bookmark Lookup in Sql Server?
body: <p>I'm in the process of trying to optimize a query that looks up historical data.  I'm using the query analyzer to lookup the Execution Plan and have found that the majority of my query cost is on something called a "Bookmark Lookup".  I've never seen this node in an execution plan before and don't know what it means.  </p>
  
  <p>Is this a good thing or a bad thing in a query?</p>