I feel my abilities as a developer really took off when I took the time to really learn SQL and take advantage of the features that my database offers. For example, learning to use window functions felt like that galaxy brain meme where you become one with the universe.

Being able to take 50 lines of ruby code (manual (anti-)joins and aggregates, result partitioning, etc...) and replace it with a couple lines of sql that is much faster and less buggy is a life changing experience.

The only other time I had such a dramatic shift in the way that I look at building applications is when I learned Scala (functional programming).