Question

我正在解决一个问题，即从任何“叶子”或孩子开始，我都可以找到孩子的兄弟姐妹和继兄弟姐妹。举一个更好的例子，如果父母A有两个孩子，并且与父母B共享一个孩子，而父母B有两个孩子，一个与父母A共享，一个与父母C共享，而父母c还有两个不与之共享的孩子。父母B，如何报告所有孩子？我尝试过使用递归和分层查询，但似乎无法正确处理。下面是表的结构和值以及到目前为止的尝试。

create table bw_parents(
parent_id char(1) primary key);


create table bw_children(
child_id number(2),
parent_id char(1),
constraint parent_id_fk FOREIGN KEY (parent_id) references bw_parents
);

insert into bw_parents values('A');

insert into bw_parents values('B');

insert into bw_parents values('C');

insert into bw_parents values('D');

insert into bw_parents values('E');

insert into bw_children values(1,'A');

insert into bw_children values(2,'A');

insert into bw_children values(2,'B');

insert into bw_children values(3,'B');

insert into bw_children values(3,'C');

insert into bw_children values(4,'C');

insert into bw_children values(5,'C');

insert into bw_children values(6,'D');

insert into bw_children values(7,'D');

insert into bw_children values(8,'E');

--hierarchical attempt
select A.parent_id, B.child_id, level
from bw_parents A
join bw_children B ON A.parent_id = B.parent_id
start with A.parent_id = 'B'
connect by nocycle prior B.parent_id = B.parent_id

--recursive with
with r as(
select parent_id, null as child_id
from bw_parents
union all 
select A.parent_id parent_id, B.child_id child_id
from bw_parents A
join bw_children B ON A.parent_id = B.parent_id)

select *
from r
where parent_id = 'B';

Answer 1

这是从给定的父级开始的简单（但可能效果不佳）的解决方案：

select     distinct child_id
from       bw_children
start with parent_id = 'A'
connect by nocycle (mod(level, 2) = 0 and child_id  = prior child_id ) or 
                   (mod(level, 2) = 1 and parent_id = prior parent_id)
;

如果必须以child_id开头，则必须在mod(level, 2)条件下将0和1切换为connect by的值；其余的保持不变。

Oracle分层问题（查找兄弟姐妹）

1 个答案: