Oracle:递归查询SQL

有部门表: ID,PID

--查询所有
select count(1) from TD t
--向下找包含自己
select count(1) from TD connect by prior ID=PID start with ID='?'
--向下找不包含自己
select count(1) from TD start with PID='?' connect by prior ID=PID
--向上找包含自己
select count(1) from TD start with ID='?' connect by prior PID=ID
--向下找包含自己
select count(1) from TD start with ID='?' connect by prior ID=PID
--向下找不包含自己
select count(1) from TD start with PID='?' connect by prior ID=PID
--查询部门下的一级子部门,并且每行后都包含自己
select * from TD start with PID='?' connect by prior PID=ID
--查询当前部门了所有一级子部门
select count(1) from TD t where t.PID='?'