语句递归查找父子关系语句
表结构及数据
1.通过根节点遍历子节点
select t.*,LEVEL from Test2 t START WITH t.parentid=0 CONNECT BY PRIOR t.id = t.parentid
2.通过子节点向根节点追溯
select t.*,LEVEL from Test2 t START WITH t.id=‘13‘ CONNECT BY PRIOR t.parentid = t.id
3.查找直接子节点（下一层）
select t.*,LEVEL from Test2 t where LEVEL = 2 START WITH t.parentid=0 CONNECT BY PRIOR t.id = t.parentid
4.查找孙节点
select t.*,LEVEL from Test2 t where LEVEL = 3 START WITH t.parentid=0 CONNECT BY PRIOR t.id = t.parentid
5.查找父节点(直接上级)
select t.*,LEVEL from Test2 t where LEVEL = 2 START WITH t.id=‘13‘ CONNECT BY PRIOR t.parentid = t.id
原文：https://www.cnblogs.com/xiaoyezi/p/9274443.html