递归查询

语法:

select ... from <TableName>
[where <Conditional-1>]
start with <Conditional-2>
connect by prior <Conditional-3>

举例:

select * from city start with root_id = 0 connect by prior id = root_id;

假设:这是一种树形数据结构,root_id来表示父节点

查询效果: 输出root_id = 0的节点和 其他所有子节点

举例2:

    select * from t2 start with id = 1 connect by prior id = root_id;

查询效果:输出所有id=1节点和其子树