Planetscale is a serverless MySQL platform - it's built for developers who just want a database and not have to worry about the stress of managing it, and it comes with a bunch of developer-centric tools like branching of databases and rolling back schema changes. Lovely.
Planetscale have recently released a free course on MySQL, which covers all of the basics. It's well written and well presented, and covers things from queries, schema and indexing.
In the modern development world everything has moved away from writing raw SQL. Most modern developers are using a framework of some sort that has abstracted away from writing SQL directly and instead uses an ORM of some flavour.
There's nothing wrong with using an ORM, but over time you will undoubtedly encounter issues which will be much easier to resolve if you have a solid understanding of what the ORM is actually doing under the hood. Every decent ORM will allow you to view the raw SQL it generates, which will give you insight on exactly what is going on. Let's be honest, we've all got ourselves confused when chaining relationships across dozens of models and not getting the data we're expecting.
If you're already comfortable with MySQL and database design then you might be interested in our Database Design Fundamentals certification. The certification will help prove your abilities to future (or current) employers and clients. 🚀