What type is INTERVAL in the function DATEPART?

Question

The code select DATEPART(month,getutcdate()) returns an integer representing the numeric month value of the current date. The value MONTH is one of a number of predefined options for the interval parameter. What is the underlying data type of that interval value?

declare @date datetime = getutcdate()
, @interval notNVarChar(16) = 'month' --what type should this be?  
                                      --Would it need quotes for assignment?

select DATEPART(@interval, @date)

Answer 1

There isn't one - you cannot parameterize it.

From the documentation:

DATEPART ( datepart , date )

datepart

Is the part of date (a date or time value) for which an integer will be returned. The following table lists all valid datepart arguments. User-defined variable equivalents are not valid.

(my emphasis)

Answer 2

You can make it parameterize by making a dynamic SQL as below:

declare @date datetime
set @date = GETDATE()
declare @option varchar(50)
declare @sql varchar(max)
SET @option = 'MONTH' --Here you can set other options like hour, second, milisecond etc..

set @sql = 'SELECT DATEPART('+ @option + ',''' + CONVERT(varchar,@date,21)+''')'


print @sql
EXEC( @sql)

Answer 3

There are lots of options available like :

day
week
hour
minute
second
millisecond

etc..

PLease go thru thisLINK