SQL Server calculates database Time Difference

Description: datediff (datepart, startdate, enddate) returns the number of datepart intervals.

Select datediff (YY, '2017-06-1 ', getdate () -- calculate the number of years
Select datediff (Q, '1970-01-1 ', getdate () -- calculate the number of quarters, three months, and one quarter
Select datediff (mm, '2017-06-1 ', getdate () -- calculate how many months
Select datediff (DD, '2017-06-1 ', getdate () -- calculate the number of days
Select datediff (wk, '2017-06-1 ', getdate () -- calculate the number of weeks
Select datediff (HH, '2017-06-10 ', '2017-06-10') -- calculate how many hours
Select datediff (n, '2017-06-10 ', '2017-06-10') -- calculate how many minutes
Select datediff (SS, '2017-06-10 10:10:00 ', '2017-06-10 10:10:10') -- calculate the number of seconds
Select datediff (MS, '2017-06-16 10:10:10 ', '2017-06-16 10:10:11') -- calculates how many milliseconds