获取每个组的前5条记录，并将它们合并到每组一行中

WITH ranked_records AS (
    SELECT
        group_id,
        record_data,
        ROW_NUMBER() OVER (PARTITION BY group_id ORDER BY some_order_column) AS rn
    FROM records
)
SELECT
    group_id,
    STRING_AGG(record_data, ', ') WITHIN GROUP (ORDER BY rn) AS merged_records
FROM ranked_records
WHERE rn <= 5
GROUP BY group_id;

CREATE TABLE records (
    group_id INT,
    record_data VARCHAR(255),
    some_order_column INT
);

INSERT INTO records (group_id, record_data, some_order_column) VALUES
(1, 'Record 1', 1),
(1, 'Record 2', 2),
(1, 'Record 3', 3),
(1, 'Record 4', 4),
(1, 'Record 5', 5),
(1, 'Record 6', 6),
(2, 'Record A', 1),
(2, 'Record B', 2),
(2, 'Record C', 3),
(2, 'Record D', 4),
(2, 'Record E', 5);

group_id | merged_records
---------|----------------
1        | Record 1, Record 2, Record 3, Record 4, Record 5
2        | Record A, Record B, Record C, Record D, Record E