SQLBolt – Interactive lessons and exercises to learn SQL
My favorite book for learning SQL is “The Art of PostgreSQL”. https://theartofpostgresql.com/I found the combination of real-world problems, general SQL advice, and the broad range of topics to be a really good book. It took my SQL from “the database is not much more than a place to persist application data” to “the application is not much more than a way to match commands to the database”. It’s amazing how much bespoke code is doing a job the database can do for you in a couple of lines.