Question

I need to get the following result between two dates:

date_start = 01/01/2010
date_end = 10/21/2012

result: 1 year, 9 months and 20 days.

I tried the code bellow, but it didn’t work. It returns negative dates sometimes:

SELECT CAST(DATEDIFF(yy, date_start, date_end) AS varchar(4)) +' year '+
       CAST(DATEDIFF(mm, DATEADD(yy, DATEDIFF(yy,date_start , date_end), date_start), date_end) AS varchar(2)) +' month '+
       CAST(DATEDIFF(dd, DATEADD(mm, DATEDIFF(mm, DATEADD(yy, DATEDIFF(yy, date_start, date_end), date_start), date_end), DATEADD(yy, DATEDIFF(yy, date_start, date_end), date_start)), date_end) AS varchar(2)) +' day' AS result

Thank You!

Answer 1

This may not correctly handle leap years if @s or @e are adjacent to them, but other than that this should be pretty close:

DECLARE @s DATE, @e DATE

SELECT @s = '20100101', @e = '20121021';

SELECT y + ' year(s), ' + m + ' month(s) and ' + d + ' day(s).'
FROM
(
  SELECT 
    RTRIM(y), 
    RTRIM(m - CASE WHEN pd < 0 THEN 1 ELSE 0 END),
    RTRIM(CASE WHEN pd < 0 THEN nd ELSE pd END)
  FROM 
  (
    SELECT
      DATEDIFF(MONTH, @s, @e) / 12, 
      DATEDIFF(MONTH, @s, @e) % 12,
      DATEDIFF(DAY, @s, DATEADD(MONTH, -DATEDIFF(MONTH, @s, @e), @e)),
      DATEDIFF(DAY, @s, DATEADD(MONTH, 1-DATEDIFF(MONTH, @s, @e), @e))
  ) AS x (y, m, pd, nd)
) AS y (y, m, d);

Output:

2 year(s), 9 month(s) and 20 day(s).

If accounting for the extra day in a leap year is crucial, I’m sure it could be adjusted to handle that. Though through minimal testing I wasn’t able to see any case where it would break (it just doesn’t feel like it should work).