You can use following to find difference between BDate and JDate
CONVERT(nvarchar, DATEDIFF(d, BDate, JDate)) + ':' + CONVERT(nvarchar, DATEDIFF(hh, BDate, JDate) % 24) + ':' + CONVERT(nvarchar, DATEDIFF(n, BDate, JDate) % 60)
SELECT
ID,
Name,
BDate,
JDate,
CONVERT(nvarchar, DATEDIFF(d, BDate, JDate)) + ':' + CONVERT(nvarchar, DATEDIFF(hh, BDate, JDate) % 24) + ':' + CONVERT(nvarchar, DATEDIFF(n, BDate, JDate) % 60) AS Difference
FROM
Temp