Dates (Transact-SQL)

DATEDIFF (Transact-SQL)

SELECT *, 
DATEDIFF(MONTH, [first_retail_availability], [discontinued]) AS diff_month
from [dbo].[console_dates] ORDER BY diff_month desc

This function returns the count (as a signed integer value) of the specified datepart boundaries crossed between the specified startdate and enddate.

See DATEDIFF_BIG (Transact-SQL) for a function that handles larger differences between the startdate and enddate values. See Date and Time Data Types and Functions (Transact-SQL) for an overview of all Transact-SQL date and time data types and functions.

DATEDIFF ( datepart , startdate , enddate )  

DATEPART (Transact-SQL)

This function returns an integer representing the specified datepart of the specified date.

select [platform_name], [first_retail_availability]
from [dbo].[console_dates] 
where DATEPART(MONTH, [first_retail_availability]) -11 = 0

select 
	[platform_name], [first_retail_availability]
from 
	[dbo].[console_dates] 
where 
	DATEPART(MONTH, [first_retail_availability]) -12 = 0 OR 
	DATEPART(MONTH, [first_retail_availability]) -11 = 0