01-数据库SQL递归查询

运用场景：树查询、多树查询、树过滤

适用范围：数据库通用

with t_data(node, parent_node) as (    values ('node-1', null),           ('node-2', 'node-1'),           ('node-3', 'node-2'),           ('node-4', 'node-3'),           ('node-a', null),           ('node-b', 'node-a'),           ('node-c', 'node-b'),           ('node-d', 'node-c')),     t_tree(node, parent_node) as (         select node, parent_node         from t_data         where parent_node is null           and node = 'node-1'         union all   --递归查询的固定结构         select n.node, n.parent_node         from t_data n,              t_tree r         where n.parent_node = r.node     )select node, parent_nodefrom t_tree;