There are a lot of good resources to learn the "how" of SQL, but not the "why". The first reason is that the relational model is a combination of logic and set

There are a lot of good resources to learn the "how" of SQL, but not the "why". The first reason is that the relational model is a combination of logic and set theory, which happens to be great for a lot of business applications. The second reason is that people have adapted SQL surprisingly well to other kinds of data, like JSON. Even if you try to build a database system specialized to JSON, it will still probably come out worse because getting things like storage, replication, administration, etc. right takes a long time. The third reason is that data has more value when combined seamlessly with other data. So if you have business data (which everyone has) and JSON, you are better off with a single system that is great at business data and OK at JSON, than two specialized systems. Keeping these things in mind makes it easier to understand SQL in my opinion.