Chad Callihan rolls up the data:
When learning T-SQL, I’d wager that learning GROUP BY comes up early in the process. What may not be mentioned are the variations that can be added to a GROUP BY clause. Are you familiar with GROUP BY GROUPING SETS, GROUP BY ROLLUP, and GROUP BY CUBE? If you’ve never seen these used, or if you have and want a refresher, read on as we look at an example of each.
Of the three, CUBE is the one that I’ve used the least. I’ve found good instances where ROLLUP gives me exactly what I want for reporting purposes, and GROUPING SETS is powerful enough that I’ve made use of it a fair number of times. But CUBE just returns back too many combinations for what I’ve needed.