[odipar]

My first encounter with 'SQL' was a course on relational algebra that was taught at my university.

It started out with defining relations as a mathematical construct, and continued with various operators on such relations. Then they continued explaining the various normal forms up the fifth normal form. I was completely out of my depth, but at least it was good and solid theory that could be learned.

What really messed with my head is they then introduced SQL as a 'practical' implementation of relational algebra. I'm still having nightmares where I try to understand nested HAVING statements that where asked at the exams.

Hey relations don't contain duplicates! But that's OK. We should call (modern) SQL 'BAG ALGEBRA'.

[geophile]

Yes, SQL is about bags, not sets.

And anything having to do with aggregation cannot be expressed in relational algebra.

[melony]

Don't forget loops