UNION

MATCH (a)-[:KNOWS]->(b)
RETURN b.name
UNION
MATCH (a)-[:LOVES]->(b)
RETURN b.name

Returns the distinct union of all query results. Result column types and names have to match.

MATCH (a)-[:KNOWS]->(b)
RETURN b.name
UNION ALL
MATCH (a)-[:LOVES]->(b)
RETURN b.name

Returns the union of all query results, including duplicated rows.