递归 CTE 结果是无限的

Question

我在 SQL 中有一个表“ActionItem”，其中包含 ActionItemId、ItemName 和 ParentActionItemId 字段。我正在创建一个存储过程，它将接受 ActionItemId (Id) 并递归显示作为 Id 子项的所有 ActionItem 记录。为此，我使用了 CTE。

ALTER PROCEDURE [dbo].[SSP_ActionItem] 
@ActionItemId int
AS
BEGIN   
WITH ActionItemList AS
(
    --  Anchor
    SELECT ActionItem.ActionItemId,
           ActionItem.ItemName,
           ActionItem.ParentActionItemId 
    FROM ActionItem 
    WHERE ActionItemId=@ActionItemId

    UNION ALL

    --  Recursive query
    SELECT AIL.ActionItemId,
           AIL.ItemName,
           AIL.ParentActionItemId  
    FROM   ActionItem AS AI INNER JOIN  ActionItemList AS AIL 
    ON AI.ParentActionItemId=AIL.ActionItemId

)
SELECT * FROM ActionItemList
--option (maxrecursion 0)
END 

表结构：

   SELECT TOP 1000 [ActionItemId]
    ,[ParentActionItemId]
    ,[ItemName]
    FROM [ActionItem]

这个 sp 返回无限记录。我不明白我哪里出错了。谁能帮忙？我是这个 CTE 概念的新手。

Answer 1

程序应该是：

ALTER PROCEDURE [dbo].[SSP_ActionItem] 
@ActionItemId int
AS
BEGIN   
WITH ActionItemList AS
(
    --  Anchor
    SELECT ActionItem.ActionItemId,
           ActionItem.ItemName,
           ActionItem.ParentActionItemId 
    FROM ActionItem 
    WHERE ActionItemId=@ActionItemId

    UNION ALL

    --  Recursive query
    SELECT AI.ActionItemId,
           AI.ItemName,
           AI.ParentActionItemId  
    FROM   ActionItem AS AI INNER JOIN  ActionItemList AS AIL 
    ON AI.ParentActionItemId=AIL.ActionItemId

)