试试这个：
WITH brumba(le_vel,root,node,id_name,root_distance) AS ( SELECt 1 as le_vel, id_name as root, null as node, id_name, to_number(null) as root_distance FROM MY_TREE WHERe parent_id IS NULL UNIOn ALL SELECt b.le_vel + 1, b.root, CASE WHEN 1 < ( SELECT count(*) FROM MY_TREE t1 WHERe t1.parent_id = t.parent_id ) THEN t.parent_id ELSE b.node END, t.id_name, coalesce(b.root_distance,0)+t.parent_distance FROM MY_TREE t JOIN brumba b ON b.id_name = t.parent_id)SELECt * FROM brumba
无需使用PL / SQL进行“第二种方法”-上面的SQL将立即计算所有根节点（
parent_id列中为空）的结果。
只需添加一个前缀或者
INSERT INTO tablename(col1,col2, ... colN) ...还是
CREATE TABLE nameAS ...以上面的查询。
上面的演示包含后一个选项的示例
CREATE TABLE xxx AS query
