Question

I have a calculated column which is updated when two other columns are updated and the formula for this column is

SELECT(datediff(day,'2012-11-01 18:15:00.000','2012-10-22 11:59:58.000'))

It works fine for all other dates but when the month changes, then I get a negative value. How can I make sure this does not happen and I get the correct integer value?

Answer 1

Well, two options:

1. just make sure the earlier date is always the first in your list of dates for DATEDIFF

   SELECT DATEDIFF(DAY, '2012-11-01 18:15:00.000', '2012-10-22 11:59:58.000')
   

   This gives you a result of -10 – this is because the first date in your list is the later date.

   If you use

   SELECT DATEDIFF(DAY, '2012-10-22 11:59:58.000', '2012-11-01 18:15:00.000')
   

   you get the result of 10 – since the first date in DATEDIFF is the earlier date.

2. just use ABS to get the absolute value (without the + or -):

   SELECT ABS(DATEDIFF(DAY, '2012-11-01 18:15:00.000', '2012-10-22 11:59:58.000'))
   

   In that case, you never get a negative value.