if bug_status went to IN BACKLOG
  then bug_status went to ASSIGNED
  and this happened 2016-03-01 to 206-03-31
  then consider valid record

set @BugID = 64252;

select
     bugs_activity.bug_id,
--   profiles.realname,
--   profiles.login_name,
     bugs_activity.bug_when,
     fielddefs.name,
     bugs_activity.added
--   bugs_activity.removed
from
     bugs_activity,
     profiles,
     fielddefs

-- Real world 'Where xx' will have more logic and result in a number of bugzilla records
-- Each bugzilla record has its own 'bugs_activity'
-- Logic needs to look at each buzilla records historyto filter results
-- Want to end up with a filtered record set and a total number of records
Where  bug_id = @BugID AND bugs_activity.who = profiles.userid AND bugs_activity.fieldid = fielddefs.id

bug_id bug_when name added
64252 26/01/2016 6:51:30 AM status_whiteboard ID:103138574
64252 26/01/2016 6:52:10 AM cc xxx@abc.com
64252 28/01/2016 9:49:10 AM bug_status IN BACKLOG
64252 28/01/2016 9:49:10 AM cf_escalation_notes Effort: 2
Reproduced by support
64252 28/01/2016 9:49:10 AM assigned_to def@abc.com
64252 2/05/2016 4:33:05 PM bug_status ASSIGNED