title: Access top n in group
body: <p>I have a table where I need to get the top n highest amount items for each Category.</p>
  
  <pre>
  Category Item  InventoryCount
  -------  ----- ------------- 
  Beverage  milk    3  
  Beverage  water   2 
  Beverage  beer    9 
  Utensil   fork    7 
  Utensil   spoon   2 
  Utensil   knife   1 
  Utensil   spork   4 
  </pre>
  
  <p>My desired output is the highest Inventory of the topmost 2 Categories. </p>
  
  <pre>
  Category Item  InventoryCount
  -------  ----- ------------- 
  Beverage  beer   9 
  Beverage  milk   3 
  Utensil   fork   7 
  Utensil  spork   4 
  </pre>