Understanding the differences between CUBE and ROLLUP

Question

My assignment asked me to find out \"how many invoices are written for each date?\"

I was a little stuck and asked my professor for help. She emailed me a query that

Answer 1

You can find more detail about GROUPING SET, CUBE, ROLL UP. TL;DR they just expand GROUP BY + UNION ALL in some ways to get aggregation :)

https://technet.microsoft.com/en-us/library/bb510427(v=sql.105).aspx