Recently, somebody shared resources to start learning deep learning [0]. It includes learning SQL. These are some recommendations:

1. Book "Head First SQL: Your Brain on SQL - A Learner's Guide" by Lynn Beighley

2. Book "Learning SQL: Generate, Manipulate, and Retrieve Data" by Alan Beaulieu

3. "Learn SQL" course from Codecademy.

You can see the full recommendation here [1].

[0]: https://news.ycombinator.com/item?id=24817630

[1]: https://awesomedataengineering.com/