如何在 SQL 服务器中的分层 table 上串联父子行？

Question

我有一个 table 地址，我想连接行，例如 parent-1 => parent-1/all-child、parent-2 => parent-2/all-child 等等....

地址Table

ID   Caption   Parent
---------------------
1    A          NULL
2    B          NULL
3    a          1
4    b          2
5    bb         4
6    C          NULL
7    aa         3
8    c          6

NULL Parent is is mean Root

期望的输出

ID   Caption   Parent
---------------------
1    A          NULL
3    A/a        1
7    A/a/aa     3
2    B          NULL
4    B/b        2
5    B/b/bb     4
6    C          NULL
8    C/c        6

Answer 1

您可以为此使用递归 cte。这个想法是从根节点开始，遍历层次结构到叶子，在你走的时候连接路径。

with cte as (
    select id, cast(caption as nvarchar(max)) caption, parent from mytable where parent is null
    union all 
    select t.id, cast(c.caption + '/' + t.caption as nvarchar(max)), t.parent
    from cte c
    inner join mytable t on t.parent = c.id
)
select * from cte order by caption

Demo on DB Fiddle:

id | caption | parent
:- | :------ | -----:
1  | A       |   null
3  | A/a     |      1
7  | A/a/aa  |      3
2  | B       |   null
4  | B/b     |      2
5  | B/b/bb  |      4
6  | C       |   null
8  | C/c     |      6