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It opens up with analyzing death row inmates, so significantly more real than classifying flowers.

Sounds like https://mystery.knightlab.com/ SQL Murder Mystery by Northwestern University Knight Lab.

It's a different area of SWE, but https://deadlockempire.github.io/ is great except the final level.

There was one about space exploration based on Postgres, but I don’t remember the name.

Mastery with SQL. A paid course that‘s excellent.

Yeah it's excellent, but I am pretty sure OP was talking about something else:

Damn, I meant Curious Moon and said the other great one.

People, do both! Worth every cent!