Lately, I've been working in SQL Server Analysis Services (SSAS).
An entire world has existed in parallel to writing SQL statements.
Theres Measures, Calculated Measures, Hierarchies, KPI Goals, Values, MDX language.
Two things I've learned so far. It's extremely powerful. It's complicated.
MDX may look like SQL, yet that's as close as it gets.
Yet the thing is, Microsoft has an alternative solution now with Tabular Models and DAX.
Should I be learning all this new stuff just to see it vanish. Hardly, this stuff is out in the wild and will need support for a long long time, as well as new clients requesting it.
However one would be smart to learn the Tabular Model. I happened to learn that first, then SSAS.
For the complete life cycle, you grab data from the relational system, into a Data Warehouse, then either SSAS or Tabular Model, then into Performance Point, Power View, Power Pivot or SSRS.
The good news, since the product is so mature, there's tons of blogs and documentation available on the web.
I first heard of Cubes / MDX in 2001 working for a company called Z-Tel. I had to write MDX queries to pull data from the cube into a Crystal Report, which I did using Wizards.
Fast forward, 12 years later, it's all starting to make sense.
And so it goes!