SQL is a programming language that is used to interact with databases.
While each database flavour will have its own implementation of SQL there are foundations in the language that will be widely applicable.
These are some resources which have proved to be very useful in getting up to speed with SQL below.
1. Socratica SQL Tutorial playlist
2. SQL Essential Training course on LinkedIn Learning
My github repository with materials: https://github.com/quincysmiith/vigilant-telegram