SQL is the standard relational data management language. We live in a data-driven world, and there are many businesses that store their information inside large, relational databases. This makes SQL a great skill not only for data scientists and engineers, but for anyone wanting to be data-literate.
If interested in learning the basics and an introduction to the SQL language, we'd recommend the Learn SQL course. To view all of the courses and Paths that teach SQL and learn more about the language, please see the SQL course catalog.