SQL DATEPART() function is used to get a part of any specific date , it could be a day, month, year or time of specific date.
It always returns an integer which is a part of a date.
Syntax
DATEPART(datepart, inputdate)
datepart is the part of a date to be extracted.
inputdate is the date from which the date part is extracted.
Lets look at an example of DATEPART() function in SQL .
DECLARE @date DATETIME = '2018-03-27 18:23:45.470'; SELECT DATEPART(year, @date) as year, DATEPART(quarter, @date) as quarter, DATEPART(month, @date) as month, DATEPART(day, @date) as day, DATEPART(dayofyear ,@date) as dayofyear, DATEPART(Week ,@date) as week, DATEPART(hour, @date) as hour, DATEPART(minute, @date) as minute, DATEPART(second, @date) as second , DATEPART(millisecond, @date) as millisecond , DATEPART(microsecond, @date) as microsecond , DATEPART(nanosecond, @date) as nanosecond
 As you can see, it returns all the part of date accordingly.
So using a datepart() function, you can get any part of date.
Below, given are the valid datepart list that you can use to get a part of date as per your requirement.
day         d, dd month        m, mm year        yy, yyyy quarter       qq, q hour         hh minute       mi, n second        ss, s millisecond    ms microsecond  mcs nanosecond   ns week        wk, ww dayofyear    dy, y
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