After I saw 
@arcange's SteemSQL some months ago and made an easy query with DBeaver I was fascinated by all the data we could pull out of it, I was hesitating to go deeper. I took some intense lessons from my friend in September but I haven't spent time to learn more about it.
I came from a marketing/online content interest but I was always fascinated by the charts and other factors which can show details of the users or whatever in the database.
Now I talked to a data analyst from Poland and I decided I would choose it as a new start in my career in the new year.
I collected some sources where you and me can pick up the skills fast enough but I am sure I will spend more time with my developer friend who can pinpoint the pitfalls of SQL. But I have to start somewhere.
Thanks to the internet you can find free courses and descriptions and I highly recommend the Steem SQL database to try your new queries.
You can dowload some apps from the Google Store or search online. I started w3school but you can find videos from youtube and maybe from other SQL courses online but the most important is to do it. The more you go deeper and try new things you will learn more. I have an understanding up till the JOINs where queries can get a bit difficult but as I said, it's all about practice.
The next step would be the visualisation of these datas but I have a long way until I can show some exciting charts but I am on it.
I also just found this site https://sqldbm.com which is free to use and I wonder what it can do.
Oh, do not forget to support/upvote @arcange because he spends around $400 every months to run SteemSQL.
The main part for SQL connection:
Host: sql.steemsql.com
Database/Schema: DBSteem
User name: steemit
Password: steemit
Every note and advice is appreciated. Thanks for following.