array_
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Collects values into an array.
Syntax
array_agg(<expr>)Arguments
| Argument | Type | Description |
|---|---|---|
<expr> | Any type | Input value. |
Returns
Returns array. Includes NULL values. Returns [] for empty input.
Usage notes
Use WITHIN GROUP ORDER BY before AGGREGATE to define element order.
Examples
Collect each session’s events in sequence, even when the input rows arrive out of order:
VALUES
('s-17', 3, 'payment_failed'), ('s-17', 1, 'cart_viewed'),
('s-17', 2, 'checkout_started'), ('s-42', 2, 'payment_completed'),
('s-42', 1, 'checkout_started')
SELECT $0 AS session_id, $1 AS sequence, $2 AS event
GROUP BY session_id
WITHIN GROUP ORDER BY sequence
AGGREGATE array_agg(event) AS journey
ORDER BY session_id+------------+-----------------------------------------------------+
| session_id | journey |
+------------+-----------------------------------------------------+
| s-17 | ["cart_viewed","checkout_started","payment_failed"] |
| s-42 | ["checkout_started","payment_completed"] |
+------------+-----------------------------------------------------+ORDER BY session_id sorts result rows; WITHIN GROUP ORDER BY sequence sorts the elements inside each array.