text: ----------------------------------------------------
  -- select from items where price is greater than the result
  -- of the nested query which is the average item price
  -- 
  -- name         | id | price
  -- -------------|----|-------
  -- 'Screen'     |5   |'275.50'
  -- 'DSLR Camera'|9   |'400.00'
  -- 
  ----------------------------------------------------
  SELECT * FROM items WHERE price >
  (SELECT AVG(items.price) FROM items);