[英]Hierarchical Query to Self-Join Table Max 3 Times
I have an Oracle DB with a table with the following columns: 我有一个带有以下各列的表的Oracle DB:
ID | PARENTID | DETAIL1
------------------------
1 | NULL | BLAH1
2 | 1 | BLAH2
3 | 2 | BLAH3
4 | 2 | BLAH4
5 | NULL | BLAH5
6 | 5 | BLAH6
7 | 6 | BLAH7
8 | 5 | BLAH8
9 | 5 | BLAH9
10 | 8 | BLAH10
I prepared a self-join for 我准备了一个自我加入
SELECT PARENT.ID AS "PID",
PARENT.DETAIL1 AS "PDETAIL1",
CHILD.ID AS "CID",
CHILD.DETAIL1 AS "CDETAIL1"
FROM table1 CHILD
LEFT OUTER JOIN table1 PARENT
ON PARENT.ID = CHILD.PARENTID
WHERE PARENTID IS NOT NULL;
The output looks as shown below: 输出如下所示:
PID | PDETAIL1 | CID | CDETAIL1|
--------------------------------
1 | BLAH1 | 2 | BLAH2 |
2 | BLAH2 | 3 | BLAH3 |
2 | BLAH2 | 4 | BLAH4 |
5 | BLAH5 | 6 | BLAH6 |
6 | BLAH6 | 7 | BLAH7 |
5 | BLAH5 | 8 | BLAH8 |
5 | BLAH5 | 9 | BLAH9 |
8 | BLAH8 | 10 | BLAH10 |
Pretty straight forward. 非常简单。 I would like to know if this self join can be done as a hierarchical/recursive query.
我想知道是否可以将这种自我联接作为层次/递归查询来完成。 The maximum nesting depth is 3. The target output should look like this:
最大嵌套深度为3。目标输出应如下所示:
GPID | GPDETAIL1 | PID | PDETAIL1 | CID | CDETAIL1 |
---------------------------------------------------
1 | BLAH1 | 2 | BLAH2 | 3 | BLAH3 |
1 | BLAH1 | 2 | BLAH2 | 4 | BLAH4 |
5 | BLAH5 | 6 | BLAH6 | 7 | BLAH7 |
5 | BLAH5 | 8 | BLAH8 | 10 | BLAH10 |
5 | BLAH5 | 9 | BLAH9 | NULL | NULL |
Google isn't helping me, there is a ton of information related to hierarchical queries, but nothing including self-joins AND hierarchical queries and most questions appear to be similar (on the surface), but nothing guiding me to what I need. Google并没有帮助我,有大量与分层查询有关的信息,但是没有任何信息(包括自我联接和分层查询),而且大多数问题在表面上看起来都是相似的,但是没有什么可以指导我满足我的需求。 I'm a SQL newbie so unless the answer is specific, I could be missing it.
我是SQL新手,因此,除非答案是特定的,否则我可能会错过它。
You just need to join
to the table one more time to get the children. 您只需要再
join
一次餐桌就可以得到孩子们。 So basically have a grandparent alias, parent alias and child alias and join
accordingly: 因此,基本上有一个祖父母别名,父别名和子别名,并相应地
join
:
select
gp.id as gpid,
gp.detail as gpdetail1,
p.id as pid,
p.detail as pdetail1,
c.id as cid,
c.detail as cdetail1
from yourtable gp
left join yourtable p on gp.id = p.parentid
left join yourtable c on p.id = c.parentid
where gp.parentid is null
there is a ton of information related to hierarchical queries, but nothing including self-joins AND hierarchical queries
有大量与分层查询有关的信息,但没有任何信息包括自我联接和分层查询
You don't need both, the hierarchical query is the self-join. 您不需要两者,层次查询是自连接。
You can get close starting with a hierarchical query like: 您可以从类似于以下的分层查询开始:
select connect_by_root (id) as gpid, connect_by_root(detail1) as gpdetail1,
prior id as pid, prior detail1 as pdetail1,
id as cid, detail1 as cdetail1,
level as lvl, connect_by_isleaf as is_leaf
from table1
start with parentid is null
connect by prior id = parentid
See the docs for what connect_by_root and connect_by_isleaf mean. 请参阅文档 ,了解connect_by_root和connect_by_isleaf的含义。 You're interested in the leaf nodes, but this:
您对叶节点感兴趣,但是:
select *
from (
select connect_by_root (id) as gpid, connect_by_root(detail1) as gpdetail1,
prior id as pid, prior detail1 as pdetail1,
id as cid, detail1 as cdetail1,
level as lvl, connect_by_isleaf as is_leaf
from table1
start with parentid is null
connect by prior id = parentid
)
where is_leaf = 1;
... doesn't get quite what you want: ...没有得到您想要的东西:
GPID GPDETA PID PDETAI CID CDETAI LVL IS_LEAF
---------- ------ ---------- ------ ---------- ------ ---------- ----------
1 BLAH1 2 BLAH2 3 BLAH3 3 1
1 BLAH1 2 BLAH2 4 BLAH4 3 1
5 BLAH5 6 BLAH6 7 BLAH7 3 1
5 BLAH5 8 BLAH8 10 BLAH10 3 1
5 BLAH5 5 BLAH5 9 BLAH9 2 1
From your sample output you don't want 5/BLAH5 in the parent columns of the last row as they are the grandparents; 从示例输出中,您不希望在最后一行的父列中使用5 / BLAH5,因为它们是祖父母。 you want the child values promoted to parent status.
您希望将子级值提升为父级状态。 You can manipulate the parent and child values a little though:
不过,您可以稍微操纵父级和子级值:
select gpid, gpdetail1,
case lvl when 2 then cid else pid end as pid,
case lvl when 2 then cdetail1 else pdetail1 end as pdetail1,
case lvl when 2 then null else cid end as cid,
case lvl when 2 then null else cdetail1 end as cdetail1
from (
select connect_by_root (id) as gpid, connect_by_root(detail1) as gpdetail1,
prior id as pid, prior detail1 as pdetail1,
id as cid, detail1 as cdetail1,
level as lvl, connect_by_isleaf as is_leaf
from table1
start with parentid is null
connect by prior id = parentid
)
where is_leaf = 1;
GPID GPDETA PID PDETAI CID CDETAI
---------- ------ ---------- ------ ---------- ------
1 BLAH1 2 BLAH2 3 BLAH3
1 BLAH1 2 BLAH2 4 BLAH4
5 BLAH5 6 BLAH6 7 BLAH7
5 BLAH5 8 BLAH8 10 BLAH10
5 BLAH5 9 BLAH9
But with only three fixed levels just joining again is simpler easier to understand... 但是只有三个固定级别,再次加入更加容易理解...
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