如何从CTE

Question

得到明显的依赖关系列表中我有一个表task_dependency看起来像下面

task_id depend_task_id 
------------------------- 
1    NULL 
2    NULL 
3    1 
4    2 
4    1 
5    4 
5    3 

我尝试运行一个查询来获取每个任务不同的任务依赖列表（包括任务本身）。

预期输出（任务列表顺序无所谓）：

task_id depend_task_list 
----------------------------------------------- 
1  1; 
2  2; 
3  1;3 
4  1;2;4 
5  1;2;3;4;5 

我有什么到目前为止

DECLARE @t TABLE (task_id INT, depend_task_id INT) 

INSERT INTO @t VALUES (1, NULL),(2,NULL),(3,1),(4,2),(4,1),(5,4),(5,3) 

;WITH AllDependency (task_id,depend_task_list) 
AS( 
    SELECT 
    task_id, 
    depend_task_list=CAST(task_id AS VARCHAR(4000)) 
    FROM @t 
    WHERE depend_task_id IS NULL 
UNION ALL 
    SELECT 
    t.task_id, 
    depend_task_list= CAST(CAST(t.task_id AS VARCHAR(10)) + ';' + depend_task_list AS VARCHAR(4000)) 
    FROM @t t 
    INNER JOIN AllDependency AS d 
     ON d.task_id = t.depend_task_id 
) 
SELECT 
    task_id, 
    (SELECT depend_task_list + ';' FROM AllDependency d2 WHERE d.task_id = d2.task_id FOR XML PATH('')) AS depend_task_list 
FROM AllDependency d 
GROUP BY task_id 
ORDER BY task_id 

电流输出：

task_id depend_task_list 
----------------------------------------- 
1   1; 
2   2; 
3   3;1; 
4   4;2;4;1; 
5   5;4;2;5;4;1;5;3;1; 

问： 哪有我得到一个独特的任务依赖列表而不使用Cursor？

SQLFiddle链接http://sqlfiddle.com/#!3/4c034/2

感谢您的任何援助。

Answer 1

好吧，试试这个查询，看看是否有帮助：

DECLARE @t TABLE (task_id INT, depend_task_id INT) 

INSERT INTO @t VALUES (1, NULL),(2,NULL),(3,1),(4,2),(4,1),(5,4),(5,3) 

;WITH CTE AS 
(
    SELECT * 
    FROM @t 
    UNION ALL 
    SELECT A.task_id, B.depend_task_id 
    FROM CTE A 
    INNER JOIN @t B 
    ON A.depend_task_id = B.task_id 
    --WHERE B.depend_task_id IS NOT NULL 
), CTE2 AS 
(
    SELECT DISTINCT task_id, ISNULL(depend_task_id,task_id) depend_task_id 
    FROM CTE 
) 
SELECT t1.task_id, 
     STUFF((SELECT ';' + CAST(t2.depend_task_id AS VARCHAR(5)) 
       FROM CTE2 t2 
       WHERE t2.task_id = t1.task_id 
       ORDER BY depend_task_id 
       FOR XML PATH('')),1,1,'') AS depend_task_list 
FROM CTE2 t1 
GROUP BY task_id 

Here是sqlfiddle测试。