-- Run only in a fresh bhylu_mysql_lab seeded from repair-seed.sql.
SET NAMES utf8mb4 COLLATE utf8mb4_0900_ai_ci;
SET SESSION sql_mode = 'STRICT_TRANS_TABLES,ONLY_FULL_GROUP_BY,ERROR_FOR_DIVISION_BY_ZERO,NO_ENGINE_SUBSTITUTION';
SET SESSION time_zone = '+00:00';
SET SESSION lc_time_names = 'en_US';
WITH RECURSIVE chain AS (
  SELECT id, name, 0 AS depth FROM volunteers WHERE mentor_id IS NULL
  UNION ALL
  SELECT v.id, v.name, c.depth + 1
  FROM volunteers AS v JOIN chain AS c ON v.mentor_id = c.id
  WHERE c.depth < 10
)
SELECT name, depth FROM chain ORDER BY id;