树表的Sql查询
我有一个树状结构的表:
I have a table with tree structure:
id parentId name
----------------
1 0 Category1
2 0 Category2
3 1 Category3
4 2 Category4
5 1 Category5
6 2 Category6
7 3 Category7
在 sql 查询结果中，我需要一个表，如:
In sql query resut I need a table like:
id parentId level name
----------------------
1 0 0 Category1
3 1 1 Category3
7 3 2 Category7
5 1 1 Category5
2 0 0 Category2
4 2 1 Category4
6 2 1 Category6
谁能帮我写ms-sql查询?谢谢！
Who can help me to write ms-sql query? Thanks!
推荐答案
扩展 a_horse_with_no_name 的答案，这展示了如何使用 SQL Server 的 实现递归 CTE(递归单记录交叉应用)与 row_number() 结合以产生问题中的确切输出.
Expanding on a_horse_with_no_name's answer, this show how to use SQL Server's implementation of recursive CTE (recursive single-record cross apply) in combination with row_number() to produce the exact output in the question.
declare @t table(id int,parentId int,name varchar(20))
insert @t select 1, 0 ,'Category1'
insert @t select 2, 0, 'Category2'
insert @t select 3, 1, 'Category3'
insert @t select 4 , 2, 'Category4'
insert @t select 5 , 1, 'Category5'
insert @t select 6 , 2, 'Category6'
insert @t select 7 , 3, 'Category7'
;
WITH tree (id, parentid, level, name, rn) as
(
SELECT id, parentid, 0 as level, name,
convert(varchar(max),right(row_number() over (order by id),10)) rn
FROM @t
WHERE parentid = 0
UNION ALL
SELECT c2.id, c2.parentid, tree.level + 1, c2.name,
rn + '/' + convert(varchar(max),right(row_number() over (order by tree.id),10))
FROM @t c2
INNER JOIN tree ON tree.id = c2.parentid
)
SELECT *
FROM tree
ORDER BY cast('/' + RN + '/' as hierarchyid)
老实说，使用 ID 本身来生成树路径"会起作用，因为我们直接按 id 订购，但我想我会插入 row_number() 函数.
相关文章