Some time ago i wrote a Rust crate to run SparQL queries on a nostr events store.
https://crates.io/crates/nostralink
Makes it possible to build pretty powerful queries:
https://codeberg.org/nostralink/nostralink/src/branch/master/sparql/content_union.rq
https://codeberg.org/nostralink/nostralink/src/branch/master/sparql/feed_followees_metadata.rq
