oracle中connect by prior的使用

https://www.cnblogs.com/wanggang-java/p/10916426.html#_labelTop
connect by主要用于父子，祖孙，上下级等层级关系的查询

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语法
{ CONNECT BY [ NOCYCLE ] condition [AND condition]… [ START WITH condition ]
| START WITH condition CONNECT BY [ NOCYCLE ] condition [AND condition]…}

– 创建表
create table employee(
emp_id number(18),
lead_id number(18),
emp_name varchar2(200),
salary number(10,2),
dept_no varchar2(8)
);

– 添加数据
insert into employee values(‘1’,0,‘king’,‘1000000.00’,‘001’);
insert into employee values(‘2’,1,‘jack’,‘50500.00’,‘002’);
insert into employee values(‘3’,1,‘arise’,‘60000.00’,‘003’);
insert into employee values(‘4’,2,‘scott’,‘30000.00’,‘002’);
insert into employee values(‘5’,2,‘tiger’,‘25000.00’,‘002’);
insert into employee values(‘6’,3,‘wudde’,‘23000.00’,‘003’);
insert into employee values(‘7’,3,‘joker’,‘21000.00’,‘003’);commit;

查询以emp_id为6开始的节点

   select emp_id,lead_id,emp_name,salary
   from employee 
   start with emp_id=6
   connect by prior lead_id=emp_id;
      **prior  后面是什么就以这个条件找上级节点**

来源：CSDN

作者：ademen

链接：https://blog.csdn.net/ademen/article/details/104310629