我有一个包含自引用InReplyTo
的表格,其中包含以下数据:
PostID InReplyTo Depth
------ --------- -----
1 null 0
2 1 1
3 1 1
4 2 2
5 3 2
6 4 3
7 1 1
8 5 3
9 2 2
我想写一个查询,它将以它的线程形式返回这些数据,以便ID = 2的帖子及其所有后代将在PostID = 3之前输出,依此类推,无限深度
PostID InReplyTo Depth
------ --------- -----
1 null 0
2 1 1
4 2 2
6 4 3
9 2 2
3 1 1
5 3 2
8 5 3
7 1 1
有没有简单的方法来实现这一目标?我能够在这个阶段修改数据库结构,那么新的hierarchy
数据类型是最简单的方法吗?或者也许是一个递归的CTE?
答案 0 :(得分:1)
-- Test table
declare @T table (PostID int, InReplyTo int, Depth int)
insert into @T values (1, null, 0), (2, 1, 1), (3, 1, 1), (4, 2, 2),
(5, 3, 2), (6, 4, 3), (7, 1, 1), (8, 5, 3),(9, 2, 2)
-- The post to get the hierarchy from
declare @PostID int = 1
-- Recursive cte that builds a string to use in order by
;with cte as
(
select T.PostID,
T.InReplyTo,
T.Depth,
right('0000000000'+cast(T.PostID as varchar(max)), 10)+'/' as Sort
from @T as T
where T.PostID = @PostID
union all
select T.PostID,
T.InReplyTo,
T.Depth,
C.Sort+right('0000000000'+cast(T.PostID as varchar(max)), 10)+'/'
from @T as T
inner join cte as C
on T.InReplyTo = C.PostID
)
select PostID,
InReplyTo,
Depth,
Sort
from cte
order by Sort
结果:
PostID InReplyTo Depth Sort
----------- ----------- ----------- --------------------------------------------
1 NULL 0 0000000001/
2 1 1 0000000001/0000000002/
4 2 2 0000000001/0000000002/0000000004/
6 4 3 0000000001/0000000002/0000000004/0000000006/
9 2 2 0000000001/0000000002/0000000009/
3 1 1 0000000001/0000000003/
5 3 2 0000000001/0000000003/0000000005/
8 5 3 0000000001/0000000003/0000000005/0000000008/
7 1 1 0000000001/0000000007/
答案 1 :(得分:0)
您正在寻找的确是recursive query。
可以找到与您的案例匹配的示例here