What roles did staff members play between '2003-04-19 15:06:20' and '2016-03-15 00:33:18'?
SELECT role_code FROM Project_Staff WHERE date_from  >  '2003-04-19 15:06:20' AND date_to  <  '2016-03-15 00:33:18'
SELECT role_code FROM Project_Staff WHERE date_from  >  '2003-04-19 15:06:20' AND date_to  <  '2016-03-15 00:33:18'
[{'role_code': 'leader'}, {'role_code': 'researcher'}]