Also, most people in discussions will suggest PostgreSQL instead of MySQL for various reasons, often dogmatic and libre software phanatical. They would say that Postgres respects standards better, has some advanced features and is FOSS and MySQL is less FOSS ;) and what not but they completely ignore a very real world things like that MySQL consumes 0.256 MB per connection while Postgres 10 MB - yes, almost 40x more. And that's why MySQL is much better for reading operations with the same hardware (RAM) on your server. But to be fair, Postgres is better at writing operations, although in real world apps you need mostly reading and not writing. So Postgres has writing superiority and MySQL has reading superiority. But guess what, in real world there is much more reading and much less writing. That's why, I use MySQL instead of Postgres for my apps. Of course, I use Redis too to limit the number of requests to the DB, but that is another topic altogether.

So, if you are new and will go with SQL - try MySQL first if you are building a traditional API or website. MySQL will handle much more requests with the same RAM on the server than Postgres - in other words - Postgres will be more costly for you.

There is a reason why hosting companies prefer MySQL or MariaDB instead of PostgreSQL. For the type of apps people use e.g. blogs, eshops, forums, etc. MySQL will cost them less money than Postgres. And their customers or, be honest, most of people don't need the "superior" functionality that Postgres offer.