I remember learning about sets in elementary school in the 60's - subsets, unions, intersections (joins) - year after year, and thinking that I would never need

I remember learning about sets in elementary school in the 60's - subsets, unions, intersections (joins) - year after year, and thinking that I would never need this. Now I've been doing data engineering since 1989 (when it was called systems integration) and all I do is work with sets. So glad I had that schooling.