title: decode multiple conditions in oracle/sql
body: <p>i have this table containing:</p>
  
  <pre><code>id number = unique per user
  code = c (calendar) or f (fiscal)
  start_month = 1 to 12
  date_created
  </code></pre>
  
  <p>what do i do to decode the period of filing:</p>
  
  <p>e.g. if a user is tagged as C and start_month = 1, then period of filing will be '3' for 1st qtr, 6 for 2nd qtr, 9 for 3rd quarter and 12 for 4th quarter.</p>
  
  <p>if a user is tagged as F and start_month =2, then period of filing will be 1st qtr = 4, 2nd qtr = 7, 3rd qtr = 10, 4th qtr = 1</p>