Oracle start with...connect by prior 实现递归查询

基本语法：

<span style="font-size:18px;"><em>select ... from <TableName>
where <Conditional-1>
start with <Conditional-2>
connect by <Conditional-3>;

<Conditional-1>：过滤条件，用于对返回的所有记录进行过滤。
<Conditional-2>：查询结果重起始根结点的限定条件。
<Conditional-3>：连接条件</em></span>

数据表结构如下：

create table table_test(
priorId number,
id number,
name varchar(5),
description varchar(10)
);

测试数据：

insert into table_test(priorId,id,name,description) values(0,1,'f','f父类');
insert into table_test(priorId,id,name,description) values(1,2,'f1','f子类1');
insert into table_test(priorId,id,name,description) values(1,3,'f2','f子类2');
insert into table_test(priorId,id,name,description) values(0,4,'F','F父类');
insert into table_test(priorId,id,name,description) values(4,5,'F1','F子类1');
insert into table_test(priorId,id,name,description) values(4,6,'F2','F子类2');

获取完整树：

select * from table_test start with priorId = 0 connect by prior id = priorId;

获取特定子树：

select * from table_test start with id = 1 connect by prior id = priorId;
select * from table_test start with id = 4 connect by prior id = priorId;

如果connect by prior中的prior被省略，则查询将不进行深层递归：

select * from table_test start with priorId = 0 connect by id = priorId;
select * from table_test start with id = 1 connect by id = priorId;