Let's start with a simple answer to what is Business Intelligence?
The simplest answer I have is: BI is all about making intelligent business decisions = Business Intelligence, sounds obvious doesn't it?
It gets even easier.
We can split Business Intelligence into two parts:
1) Business Decisions - which essentially is any decision that impacts the business, for the good or for the bad.
2) Intelligence - Google definition is "Intelligence is the ability to acquire and apply knowledge and skills", and that is a brillaint definition!
When we combine it together we get something like this "BI is the ability to acquire and apply knowledge and skills that helps business make best possible decisions."
Can we measure Business Intelligence score?
Yes we can, Instead measuring people's BI Score I will refer to Business BI Score as in most cases it's more than one person, sometimes dozens or hundrends, that provide necessary knowledge and skills.
If a business has people with lot of knowledge and skills and can apply it to help business make great decisions that the business has high BI score (similar to high IQ), if not then business has low BI Score (similar to low IQ).
Bear in mind that knowledge and skills are very important, however "apply" is key, if business is not able to apply this then it's useless, and the business BI score is low.
In essence career in BI is about helping business get a high BI score.
How to measure Business BI Score?
Before we talk about knowledge, skills and how to apply those to make better decisions, let's start with something that we can potentially measure in a easy way (Feel free to refine this to your own liking).
Let's go with the same scale as IQ and set max as 200 (Genius).
175 to 200 - Business decisions are perfect with no side affects, and take very little time.
150 to 174 - Best decisions are made with little risks and decisions are relatively quickly made.
125 to 149 - Decisions are reasonably good, but limited to only "known" options, there are risks and it take time to make the decision.
100 to 124 - Decision are unreliable, sometimes good and sometimes not so good, it takes considerable effort to make a decision.
75 to 99 - Decisions are based on unreliable "facts" taken out of context, that lead to risky or unpredictable effects.
<75 - Decisions are risky and critical decision may have a significant negative impact on the company.
What is your role in BI?
People in BI provide knowledge, skills and apply them to help business make great decision, this is the end result, this is how you can measure if your role makes a difference.
Is career in BI for you?
There are so many different roles in BI, that is likely that you will find something suitable, and good news is that you have a lot of options, that includes not just promotions and but move to a different role that is a better fit for you, as very often salary is similar for most roles at the same level of experience (may vary), so you can often simply choose your dream role, which you can usually change at later point.
Another great things about BI is that it is essentially "industry independant", and that means most of your knowledge and skills will apply to all industries, so you have an option to specialize in a specific industry and make it your forte or just go from one industry to another, which can be very suitable for those who like a change.
BI, Analytics and Data Warehousing
Career in Business Intelligence is often split into Buisness Intelligence, Analytics and Data Warehousing. Business Intelligence is an "umbrella" term and you can do BI with a data warehouse or without a data warehouse, if typically a lot of technical knowledge and skills is needed for data warehousing.
We also have analytics which is more focused on business user or "Power Users" that use analytical decision to make better decisions. It includes technical knowledge but there is a lot of business knowledge needed to make sense out of data and make decisions, so it's most suitable for analytics minds.
Business Intelligence with Microsoft Tools
You will need BI tools and you have to choose one or several vendors. When I started my career in BI, I did a lot of research and decided that I will invest my future with Microsoft, as in the long term they should be fine. I'm glad it turned out like this, as Microsoft is now taking over the world and you will see that most jobs on the market are for Microsoft BI tools like SQL Server with BI Stack (SSIS, SSRS, SSAS) and in recent years Power BI which was a missing critical puzzle, and demand for BI has increased considerably and most likely will grow much more.
Below is a list of tools available from Microsoft
Extract Transform and Load (ETL) - T-SQL, SSIS or Power BI
Semantic Model (Cubes) - SSAS Multidimension, SSAS Tabular or Power BI
Reporting - SSRS or Power BI
Sharing - Power BI Online Service, Report Manager (SSRS) or Sharepoint.
Master Data Management - MDS. I wouldn't use it for Operational MDM, but would consider for Analytics MDM.
Azure / Cloud - Cortana Analytics - a lot of things are moving here, but essentially it's the same but in the cloud with it's interesting benefits.