PRAGMA YqlSelect = 'force';

WITH
    edges AS (
        SELECT src, dst
        FROM (VALUES (1, 2), (1, 3), (2, 3), (3, 4)) AS x(src, dst)
    ),
    RECURSIVE paths AS (
        SELECT 1 AS node, 0 AS depth
        UNION ALL
        SELECT e.dst AS node, p.depth + 1 AS depth
        FROM edges AS e
        INNER JOIN paths AS p ON e.src = p.node
    )
SELECT node, Min(depth)
FROM paths
GROUP BY node
ORDER BY Min(depth);