TSQL Playing with aggregates part 1

One of the least understood functionalities in TSQL is the usage of aggregates. In this article I want to back to the basics. For my examples I’m using the AdventureWorks 2012 DW:

The most basic aggregates are count and sum. How many or how much do I have:

For an information point of view these number don’t tell much. Most of the time one is interested in amount per category. A category can be something like period, customer, product, salesrep etc. Most querys have a period based axis.

This introduces the “GROUP BY” part. As you can see the results aren’t ordered. For that we have to a an “ORDER BY”.

Both the “GROUP BY” and the “ORDER BY” work for the whole set. In part 2 of this series I will show you how to make them work for subsets.

Till Next Time