Ask HN: Postgres Primer for Programmers Recommendations?

I've avoided DB's for the most part for years. I get the basic SQL statement, but nothing advanced. I'm playing with some modeling using TimescaleDB and I think it's clear I'm going to need to understand this stuff a lot better. I'm curious what literature other programmers would suggest for really getting your head around SQL. I'm less interested in the "learn by example" approach where you see a SELECT followed by a FILTER followed by an ORDER example. I want to understand better what's really going on under the hood. I'm trying to put together some MATERIALIZED VIEWS for run detection and GPT just really isn't working well for me on this kind of effort.