I wasn't comfortable recommending existing SQL tutorials to any friends or customers, especially for the non-engineers. It's such an important tool to learn that I've made a crack and making it much more approachable, both in the writing style and in the tool (SQLBox) embedded in the page that lets readers follow along with writing SQL against a live PostgreSQL instance with no setup required.
There are challenges built in and practice sections at the end of each segment. Any feedback/corrections/suggestions are hugely appreciated.
More on why I wrote it here: https://medium.com/@__dave/why-i-wrote-yet-another-sql-tutor...