One thing I never understood is that the SQL language, and its alternatives, share the same theoretical IR -- the relational algebra -- it shouldn't be that difficult to implement for postgres/mysql alternative relational languages like QUEL or Datalog. Or even just a simplified SQL with a sane, consistent syntax.

I know PG has a bunch of procedural-language alternatives, but afaik, no relational-language alternatives.

At the same time, I'd also expect it to not be that difficult to transpile from say mysql to postgres, yet there's very little in that space, at least in open source (there is however many ORMS that map to either mysql or postgres..)

Both of which, amongst the procedural-languages, you'd find a hundred transpilers (JS->C) and VM-languages (Clojure,Scala,etc on jvm) implemented even by bored/curious students. Which makes my suspicion that there's no technical blocker, just a cultural one.

That is, QUEL losing to SQL, such that you can't find any implementation, is an absurd concept -- it should be available on postgres (perhaps requiring some special starting keyword) -- but somehow it is not.

The original query language for Postgres95 was QUEL.

libpq refers to PostQUEL.

Ingres became Post-Ingres which became POSTGRES which became Postgres95 which became PostgreSQL.

https://www.postgresql.org/docs/12/history.html