我有一张数据表。
ID ParentID NodeName
1 NULL Administration
2 NULL Master Data
3 NULL Input Forms
4 NULL User Reports
5 NULL Other Pages
6 1 Add User
7 2 Product Maintanence
8 2 Product BOM
9 3 Expected Sales
10 3 Product BOM
11 4 Finance
12 4 Manufacturing
13 6 GOGS Report
14 7 Purchase History
15 8 Production Report
16 5 Google
17 5 Company Site
现在我想编写一个查询，根据父子关系区分上述查询结果，如Parent_Original＆gt;＆gt; Parent1＆gt;＆gt; Child。如果数据库子级上升到n级别，它也会导致父级n>父n-1>父n-2> ...＆gt;最后一个孩子。
在上表情景中，结果如下。
Parent Parent-1 Child
Administration Add User GOGS Report
Master Data Product Maintanence Purchase History
Master Data Product BOM Production Report
........... so on
任何人都可以建议我怎样才能做到这一点。任何建议都非常感谢。
答案 0 :(得分：3)
有两种方法可以解决这个问题。如果您需要自己列中每个关系的数据，并且关系数量不会超过x级别深度（例如，5），那么您可以在单个查询中多次连接同一个表（请参阅查询1）
如果您不需要单独列中的数据，但可以使用单个分隔值（例如，“root parent - ＆gt; next parent - ＆gt; last parent - ＆gt; child”），那么您可以使用用于构建连接字符串的CTE查询（请参阅查询2）。
declare @tbl table (id int, parentid int, nodename varchar(20))
insert into @tbl values
(1, NULL, 'Administration'),
(2, NULL, 'Master Data'),
(3, NULL, 'Input Forms'),
(4, NULL, 'User Reports'),
(5, NULL, 'Other Pages'),
(6, 1, 'Add User'),
(7, 2, 'Product Maintanence'),
(8, 2, 'Product BOM'),
(9, 3, 'Expected Sales'),
(10, 3, 'Product BOM'),
(11, 4, 'Finance'),
(12, 4, 'Manufacturing'),
(13, 6, 'GOGS Report'),
(14, 7, 'Purchase History'),
(15, 8, 'Production Report'),
(16, 5, 'Google'),
(17, 5, 'Company Site'),
(18, 13, 'Archived Data'),
(19, 13, 'Active Data'),
(20, 18, 'On Tape'),
(21, 18, 'On Disc')
/* query 1 */
select r.nodename as root
,c1.nodename as [child-1]
,c2.nodename as [child-2]
,c3.nodename as [child-3]
,c4.nodename as [child-4]
,c5.nodename as [child-5]
from @tbl r
left outer join @tbl c1 on r.id = c1.parentid
left outer join @tbl c2 on c1.id = c2.parentid
left outer join @tbl c3 on c2.id = c3.parentid
left outer join @tbl c4 on c3.id = c4.parentid
left outer join @tbl c5 on c4.id = c5.parentid
where r.parentid is null
order by r.nodename, c1.nodename, c2.nodename, c3.nodename, c4.nodename, c5.nodename
/* query 2 */
;with cte(id, parentid, nodename) as (
select id, parentid, cast(nodename as varchar(max))
from @tbl
where parentid is null
union all
select t.id, t.parentid, cast(cte.nodename + ' -> ' + t.nodename as varchar(max))
from @tbl t
inner join cte on t.parentid = cte.id
)
select nodename
from cte c1
where not exists (
select 1
from cte c2
where c1.id = c2.parentid
)
order by nodename
root child-1 child-2 child-3 child-4 child-5
-------------------- -------------------- -------------------- -------------------- -------------------- --------------------
Administration Add User GOGS Report Active Data NULL NULL
Administration Add User GOGS Report Archived Data On Disc NULL
Administration Add User GOGS Report Archived Data On Tape NULL
Input Forms Expected Sales NULL NULL NULL NULL
Input Forms Product BOM NULL NULL NULL NULL
Master Data Product BOM Production Report NULL NULL NULL
Master Data Product Maintanence Purchase History NULL NULL NULL
Other Pages Company Site NULL NULL NULL NULL
Other Pages Google NULL NULL NULL NULL
User Reports Finance NULL NULL NULL NULL
User Reports Manufacturing NULL NULL NULL NULL
nodename
------------------------------------------------------------------------
Administration -> Add User -> GOGS Report -> Active Data
Administration -> Add User -> GOGS Report -> Archived Data -> On Disc
Administration -> Add User -> GOGS Report -> Archived Data -> On Tape
Input Forms -> Expected Sales
Input Forms -> Product BOM
Master Data -> Product BOM -> Production Report
Master Data -> Product Maintanence -> Purchase History
Other Pages -> Company Site
Other Pages -> Google
User Reports -> Finance
User Reports -> Manufacturing