Difference between bigquery sql and other sql to write hierarchy sql I. 계층형 데이터(Hierarchical data) WITH employee AS ( SELECT 40 AS id , 'london' AS name, 50 AS boss_id UNION ALL SELECT 50 AS id , 'lee' AS name, 10 AS boss_id UNION ALL SELECT 10 AS id , 'harry' AS name, 20 AS boss_id UNION ALL SELECT 20 AS id , 'leo' AS name, NULL AS boss_id UNION ALL SELECT 70 AS id , 'lucas' AS name, 10 AS boss..