How to Use Array Functions in ClickHouse

Last updated July 25, 2026 · By the SaturnSQL team

arrayJoin expands an array into one row per element, arrayMap applies a lambda to each element, and has() checks membership. Arrays are first-class in ClickHouse, so these often replace joins against child tables.

SELECT user_id, arrayJoin(tags) AS tag
FROM events
WHERE notEmpty(tags);

SELECT arrayMap(x -> x * 2, [1, 2, 3]) AS doubled;

SELECT count()
FROM events
WHERE has(tags, 'checkout');