DateDiff of MS SQL system functions

DateDiff is commonly used to calculate date difference functions, using the following syntax:

DATEDIFF (DatePart, StartDate, EndDate)

Where parameter datepart has the following options (only common parameters are listed):

DatePart	Abbreviation	Explain
Year	Yy,yyyy	Years
Month	Mm,m	Month
Day	Dd,d	Days
Week	Wk,w	Week
Hour	hh	Hours
Minute	Mi,n	Minutes
Second	Ss,s	Seconds
Millisecond	Ms	Milliseconds

The following examples illustrate:

• Calculate the number of years between two dates

SELECT DATEDIFF (year,'2014-01-01', GETDATE ()) as years

You can also use an abbreviated form

SELECT DATEDIFF (YY,'2014-01-01', GETDATE ()) as years

Or

SELECT DATEDIFF (YYYY,'2014-01-01', GETDATE ()) as years

return result 3

• Calculate the number of months between two dates

SELECT DATEDIFF (MONTH,'2017-01-01', GETDATE ()) as MONTHS

Return result 5

Other types of usage are about the same, not much more.

DateDiff of MS SQL system functions