返回自联接表上的父/子关系

让所有的孩子 @ParentId 以这种方式存储可以使用递归CTE。

declare @ParentId int
--set @ParentId = 1

;WITH T AS
(
select 1 AS ID,null AS ParentId, 'Root' as [Name] union all
select 2,1,'Child of Root' union all
select 3,2,'Child of Child of Root'
),
cte AS
(
SELECT ID, ParentId, Name
FROM T 
WHERE ParentId = @ParentId  OR (ParentId IS NULL AND @ParentId IS NULL)
UNION ALL
SELECT T.ID, T.ParentId, T.Name
FROM T 
JOIN cte c ON c.ID = T.ParentId
)
SELECT ID, ParentId, Name
FROM cte
OPTION (MAXRECURSION 0)