Gremlin
The graph query language of Apache TinkerPop — describing a walk through nodes and edges, one step at a time.
Where SQL is declarative, Gremlin is fundamentally imperative: you chain steps like g.V().has('name','Alice').out('knows').out('knows'), meaning "start at Alice, follow knows two hops". Each step takes a stream of elements in and emits a stream out.
TinkerPop is an abstraction layer, so the same query can run against JanusGraph, Amazon Neptune, OrientDB and others. The main rival is Cypher from Neo4j, which is declarative and easier for many to read — but tied to fewer engines.