nurse | blockfloor | blockcode |     oncallstart     |      oncallend
-------+------------+-----------+---------------------+---------------------
   101 |          1 |         1 | 2008-11-04 11:00:00 | 2008-11-04 19:00:00
   101 |          1 |         2 | 2008-11-04 11:00:00 | 2008-11-04 19:00:00
   102 |          1 |         3 | 2008-11-04 11:00:00 | 2008-11-04 19:00:00
   103 |          1 |         1 | 2008-11-04 19:00:00 | 2008-11-05 03:00:00
   103 |          1 |         2 | 2008-11-04 19:00:00 | 2008-11-05 03:00:00
   103 |          1 |         3 | 2008-11-04 19:00:00 | 2008-11-05 03:00:00