So, here are two different relational database links that I am currently interested in.
The first is PostgreSQL Exercises. This is a fun way to sharpen your SQL. While I’m not a big user of PostgreSQL, I have enjoyed it the few times I’ve touched it. And the basics of thinking in SQL are useful across any database.
The second is Modern SQL. I was pointed to this site (in particular this page on pivots) after asking a question on a slack (so I can’t link to it). My question was about how to transform a set of event values (X happened Y ago, then Z happened at Y+1, and so on) up into counts (X happened N times, Z happened M times). But the entire site is worth reading if you are a SQL nerd, especially the use cases.
Bonus, check out this Twitter thread about using a single SQL database as a data source for multiple microservices. Pragmatism!