title: Find 2nd maximum start_date for a group of set_id in big query
body: <p>I have a table with data like below</p>
  
  <p><img src="https://i.stack.imgur.com/J5mPI.png" alt="enter image description here"></p>
  
  <p>I want the 2nd highest start date for each set where the status is C.
  e.g
  the answer should be</p>
  
  <p>1      2015-05-01<br>
  2      2015-05-01<br>
  3      2015-06-01     </p>
  
  <p>Is there a simpler way to do this in bigquery?</p>