Of course the absolute easiest way of doing it is
WHERE YEAR([date]) = 2015
But that's not sargable. It doesn't matter if you're looking at only a few thousand rows in your table. But if your table has hundreds of thousands or millions of rows, then performance will suffer greatly.
I would argue that it does matter. There is an adage that "If you fail to plan, you plan to fail." This is very applicable to this situation, because using the SARGable method plans for growth, whereas the non-SARGable method does not.
Drew
I should have been more precise in my wording.
"If you have a lower number of records, and you KNOW the number of records will not be increasing significantly, then you can use a non-Sargable function."
You may be aware of the trade offs and willing to sacrifice performance in a given situation, but another person may not and may come along and copy your code where the performance loss is not acceptable.
Also, it's highly unlikely that, when working with dates, the number of records will not be increasing significantly.
Laziness is not an acceptable excuse for sacrificing performance.
Drew
+1000000 to that!!! If you "practice" doing it the wrong way, you'll never get good at doing it the right way.