Typically, if you were writing your hypothetical sql client in rc shell, you'd implement an interface that looks something like:

    <>/mnt/sql/clone{
        echo 'SELECT * from ...' >[1=0]
        cat /mnt/sql/^`{read}^/data # or awk, or whatever
    }

This is... I don't know. I don't get why I would care to sling SQL over a file system versus a network socket.

I mean, Postgres could offer an SSH interface as a dumb pipe to psql to just have you push text SQL queries in your application. But it doesn't, it offers a binary protocol over a network socket. All the database engines have had the same decision point and have basically gone down the same path of implementing a wire protocol over a persistent socket connection.

So yeah, I don't get what doing things this way would give me as either a service provider or a service consumer. It looks like video game achievements for OS development nerds, "unlocked 'everything is a file'." But it doesn't look like it actually enables anything meaningful.