title: SQL query to find top n values for a column for a specific type of data set
body: <p>I have with me some data - Sales data for different companies for different years.
  So I have company <code>ID</code>, <code>Year</code> and <code>Sales</code> of that company (for that year).</p>
  
  <p>What I want is to obtain the <code>TOP n</code> values of sales, and corresponding company <code>ID</code> and <code>Year</code>, for each company that has data.</p>
  
  <p>There are other queries in SO but they are for straight forward <code>TOP n</code> values for a single column (without conditions like the one required here). </p>
  
  <p>Any help would be appreciated...</p>