Finding nodes that do not have specific relationship (Cypher/neo4j)

Question

I have a neo4j db with the following:

a:Foo
b:Bar

about 10% of db have (a)-[:has]->(b)

I need to get only the nodes

Answer 1

This also works if you're looking for all singletons/orphans:

MATCH (a:Foo) WHERE not ((a)--()) RETURN a;

Answer 2

That would be

MATCH (a:Foo) WHERE not ((a)-[:has]->(:Bar)) RETURN a;