I myself made a simple query language out of necessity. My key-value CRDT store [1] needed some syntax for basic queries.
It was strictly minimalistic, like {type:fruit} would produce [{type:fruit name:banana}...] and so on. When I think how to evolve it I lean towards adding lisp-like expression support. Cause I have a small lisp readily available.
I wonder if there is a good birds-eye FAQ/HOWTO/overview of all the existing (families) of query languages. Just to systematize Datalog, GraphQL, SQL, there are tons of them.