gbase8s递归

在从oracle迁移至gbase8s时 ，oracle 的with as 递归并不支持，可以修改为其他写法，例如

create table tpath(s_path varchar(50),p_path varchar(50));

insert into tpath values('/',null);
insert into tpath values('/opt','/');
insert into tpath values('/mnt','/');
insert into tpath values('/data','/');
insert into tpath values('/opt/gbase','/opt');
insert into tpath values('/opt/oracle','/opt');
insert into tpath values('/data/gbase','/data');
insert into tpath values('/data/oracle','/data');
insert into tpath values('/root','/');

oracle下的递归为 

select * from tpath start with p_path='/opt' connect by prior p_path=s_path;

或者

with a(p_path,s_path) as (select p_path,s_path from tpath where p_path='/opt'
union all 
select b.p_path,b.s_path from a,tpath b where a.p_path = b.s_path
) 
select * from a;

而在gbase8s中只支持第一种

在迁移的过程中要仔细的对比二者结果集差异，包括是否存在递归循环，有时需要稍微调整下，connect by 与 with as 并不是完全等效