yes exactly, It is the index the first and second column

Cool!

what is the benefit of using rank() vs row_num() ?

I enjoyed the NULLIF inside COALESCE. Congrats!

I totally didnt realize this is a slicing practice so my code was 17lines.
Yours is amazing.

same here.
I do find descriptions of SQL tasks bit cryptic.

Nice One!!

From PostgreSQL 14 documentation, 7.2.5:
Currently, window functions always require presorted data, and so the query output will be ordered according to one or another of the window functions' PARTITION BY/ORDER BY clauses. It is not recommended to rely on this, however. Use an explicit top-level ORDER BY clause if you want to be sure the results are sorted in a particular way.
https://www.postgresql.org/docs/14/queries-table-expressions.html

When refactoring, anything can change. I don't see this as a good reason to avoid numbers in a group by.

Using numbers in GROUP BY clause is a real bad practice. The order of columns can change which can break the code.

woow so maybe the directions could have just said order randomly instead of that crappy wording they used

No it won't. https://www.citusdata.com/blog/2016/10/12/count-performance/

Tried this and failed for me too.