title: oracle sql get last Sunday and last Saturday
body: <p>I will calculate last Sunday and last Saturday on every Monday.</p>
  
  <p>E.g. today is 08 July 2013 Monday</p>
  
  <p>last Sunday: 30 June 2013 00:00:00</p>
  
  <p>last Saturday: 6 July 2013 23:59:59.</p>
  
  <p>Note the last Sunday is from 00:00:00 and last Saturday is until 23:59:59</p>