sql - 分层查询（如何检索中间节点）

Question

晚上好，我需要帮助尝试从我的一个分层表（红色圆圈）中检索中产阶级经理，这些表既不是根节点也不是叶节点。

分层图表/数据

我能够使用我的查询检索所有叶节点

select level,  first_name ||' '|| last_name "FullName" 
from more_employees
where employee_id not in (select NVL(manager_id, 0) from more_employees)
start with employee_id = 1
CONNECT by prior employee_id = manager_id;

我确定我应该在 where 子句中使用关键字“in”，但会不断得到不同的结果。

Answer 1

我相信这样的事情应该有效

select * from more_employees m1 where manager_id is not null
and exists ( select 1 from more_employees m2 where m2.manager_id=m1.employee_id)

Answer 2

您可以CONNECT_BY_IS_LEAF为此使用伪列。

select level,  first_name ||' '|| last_name "FullName" 
from more_employees
where connect_by_isleaf = 0 and manager_id is not null
start with employee_id = 1
connect by prior employee_id = manager_id;

您还可以使用它来获取所有叶子：

select level,  first_name ||' '|| last_name "FullName" 
from more_employees
where connect_by_isleaf = 1
start with employee_id = 1
connect by prior employee_id = manager_id;

这可能比您使用子选择的解决方案更快

这是一个 SQLFiddle 示例：http ://sqlfiddle.com/#!4/511d9/2