在单表中用pid字段表示父节点id,查询时要求根据id查找某节点及其所有子节点。
测试的表结构如下:
create table test2( id integer, name varchar, pid integer );
插入测试数据
insert into test2 values(1,'A',null); insert into test2 values(2,'A1',1); insert into test2 values(3,'A2',1); insert into test2 values(4,'B',2);
树结构如下:
1 A
2 ----A1
3 --------B
4 ----A2
根据节点ID查父节点及其所有子节点的简单查询(例如查id=2的节点)
with recursive t(id, name, pid) as ( select id, name, pid from test2 where id=2 union all select t2.id, t2.name, t2.pid from test2 t2 join t on t2.pid=t.id ) select id, name, pid from t order by id;
带路径及树节点深度的查询
with recursive t(id, name, pid, path, depth) as ( select id, name, pid, array[id] as path, 1 as depth from test2 where pid is null union all select t2.id, t2.name, t2.pid, t.path || t2.id, t.depth + 1 as depth from test2 t2 join t on t2.pid=t.id ) select id, name, pid, path, depth from t order by path;