GROUP BY and HAVING

When a result contains aggregates without an explicit GROUP BY, nonaggregate projected expressions that refer to input values become grouping keys.

MATCH (p:Person)
OPTIONAL MATCH (p)-[:Knows]->(friend)
RETURN p.name AS name, COUNT(friend) AS friends
GROUP BY name ORDER BY name;

This returns Alice: 1, Bob: 1 and Cara: 0. COUNT(friend) ignores the null optional binding.

Explicit GROUP BY accepts binding variables, including output aliases. Grouping an element groups its identity while retaining the columns needed for property access. GROUP BY () chooses one global group.

SELECT COUNT(*) AS people FROM social MATCH (p:Person)
GROUP BY () HAVING COUNT(*) > 0;

SELECT HAVING filters completed groups. Ungrouped input references and nested aggregate calls are rejected. An empty global aggregate still returns one row: COUNT is 0, COLLECT_LIST is an empty list, and numeric aggregates are null.

Aggregate functions →