[英]Connect by prior get parents and children
我正在研究使用按先连接的查询。 我写了一个查询,检索实体的所有子级。 我想要的是检索孩子和父母的行。
这是我的SQL:
Select *
From myTable tab
Connect By Prior tab.id= tab.child_id
Start With tab.id= 2;
我该如何找回父母? 谢谢。
使用UNION ALL
组合一个查询来获得子项,再通过一个查询来获得祖先。
Oracle 11g R2架构设置 :
CREATE TABLE myTable ( id, child_id ) AS
SELECT 0, 1 FROM DUAL UNION ALL
SELECT 1, 2 FROM DUAL UNION ALL
SELECT 2, 3 FROM DUAL UNION ALL
SELECT 3, 4 FROM DUAL UNION ALL
SELECT 4, 5 FROM DUAL UNION ALL
SELECT 3, 6 FROM DUAL UNION ALL
SELECT 0, 7 FROM DUAL UNION ALL
SELECT 1, 8 FROM DUAL;
查询1 :
SELECT * -- Child Rows
FROM mytable
START WITH id = 2
CONNECT BY PRIOR child_id = id
UNION ALL
SELECT * -- Ancestor Rows
FROM mytable
START WITH child_id = 2
CONNECT BY PRIOR id = child_id
结果 :
| ID | CHILD_ID |
|----|----------|
| 2 | 3 |
| 3 | 4 |
| 4 | 5 |
| 3 | 6 |
| 1 | 2 |
| 0 | 1 |
如果您使用的是11gR2或更高版本,则分层查询的另一种方法是递归子查询分解 :
with rcte (id, child_id, some_other_col) as (
select id, child_id, some_other_col -- whichever columns you're interested in
from myTable
where id = 2
union all
select t.id, t.child_id, t.some_other_col -- whichever columns you're interested in
from rcte r
join myTable t
on t.id = r.child_id -- match parents
or t.child_id = r.id -- match children
)
cycle id set is_cycle to 1 default 0
select id, child_id, some_other_col -- whichever columns you're interested in
from rcte
where is_cycle = 0;
锚成员找到您的初始目标行。 然后,递归成员将查找到目前为止找到的每一行的父母或孩子。
最终查询可以获取所需的任何列,进行汇总等。
(当然,可能值得用真实数据测试这两种方法,以查看是否存在性能差异)。
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