Question

We messed up on application side and loaded some incorrect data in one column.. Now we need to fix this data.. Here is what we need to do.

Starttime                      Answertime

2012-08-30 00:40:40.000      2012-08-30 03:40:53.000

Answertime is almost 3 hour more than starttime which is incorrect. Now what we need to is find the difference of seconds between answertime and startime and add it to starttime. So for above 2012-08-30 00:40:53.000 will be new answertime.

Kind of confused at the moment on how to do it. Using sql server 2008 R2

Answer 1

declare @t table (
  Starttime datetime,
  Answertime datetime);
insert @t values (
  '2012-08-30 00:40:40.000','2012-08-30 03:40:53.000'),(
  '2012-08-30 00:59:59.900','2012-08-30 03:00:03.000');

update @t set Answertime =
  case when dateadd(hh,datediff(hh,answertime,starttime),answertime) > starttime
       then dateadd(hh,datediff(hh,answertime,starttime),answertime)
       else dateadd(hh,datediff(hh,answertime,starttime)+1,answertime) end
where Answertime > DateAdd(hh,1,StartTime); -- more than 1 hour apart

select * from @T;

>>
STARTTIME                   ANSWERTIME
August, 30 2012 00:40:40    August, 30 2012 00:40:53
August, 30 2012 00:59:59    August, 30 2012 01:00:03

The gist of the answer is that leaving Minutes:Seconds.MilliSecs aside, the answertime is put into the same hour as the starttime. It also fixes edge cases like the 2nd row where the change makes it earlier than the starttime.