想要知道所有可能的父母和子行對特定的ID？

Question

如何知道所有可能的父級和子行鍼對特定的ID？

例如有如下表：

MyTable的：

----------------------------------------------------- 
| Id | PId | Description    | 
----------------------------------------------------- 
| 1 | NULL | A is Parent    | 
| 2 |  1  | B is Child of A   | 
| 3 |  2  | C is Child of B   | 
| 4 | NULL | D is Parent    | 
| 5 | NULL | E is Parent    | 
| 6 |  5  | F is Child of E   | 
----------------------------------------------------- 

想知道的所有可能的父母和孩子，當通spesific ID

例如

CASE-01：

當@ MyLookupId = 2 OR @ MyLookupId = 1 OR @ MyLookupId = 3一個從他們然後結果應該是，

------- 
| Id | 
------- 
| 1 | 
| 2 | 
| 3 | 
------- 

CASE-02：

當@ MyLookupId = 4然後結果應該是，

------- 
| Id | 
------- 
| 4 | 
------- 

CASE-03：

當@ MyLookupId = 6然後結果應該是，

------- 
| Id | 
------- 
| 5 | 
| 6 | 
------- 

下面是表的SQL：

IF OBJECT_ID('tempdb.dbo.#MyTable', 'U') IS NOT NULL DROP TABLE #MyTable; 
SELECT * INTO #MyTable FROM (
    SELECT (1)Id, (NULL)PId, ('A IS Parent')Description UNION ALL 
    SELECT (2)Id, (1)PId, ('B IS Child of A')Description UNION ALL 
    SELECT (3)Id, (2)PId, ('C IS Child of B')Description UNION ALL 
    SELECT (4)Id, (NULL)PId, ('D IS Parent')Description UNION ALL 
    SELECT (5)Id, (NULL)PId, ('E IS Parent')Description UNION ALL 
    SELECT (6)Id, (5)PId, ('F IS Child of E')Description) AS tmp 

SELECT * FROM #MyTable 

Answer 1

通過TRIV作品給出的答案，但需要每次計算源表的整個層次結構e查詢運行，可能無法在較大規模下執行。

更窄的辦法是找父母與子女的記錄，只有涉及到ID您正在搜索：

declare @t table(ID int, PID int); 
insert into @t values(1,null),(2,1),(3,2),(4,null),(5,null),(6,5); 

declare @ID int = 2; 

with c as 
(
    select ID 
      ,PID 
    from @t 
    where ID = @ID 

    union all 

    select t.ID 
      ,t.PID 
    from @t t 
     join c 
      on(t.PID = c.ID) 
) 
,p as 
(
    select ID 
      ,PID 
    from @t 
    where ID = @ID 

    union all 

    select t.ID 
      ,t.PID 
    from @t t 
     join p 
      on(t.ID = p.PID) 
) 
select ID 
from p 

union all 

select ID 
from c 
where c.ID <> @ID 
order by ID; 

輸出：

ID 
```` 
1 
2 
3 

Answer 2

你可以使用recursive cte

-- temp returns full tree of each rootId (parentid = null) 
;WITH temp AS 
(
    SELECT sd.Id, sd.PId, sd.Id AS RootId 
    FROM #MyTable sd 
    WHERE sd.PId IS NULL 

    UNION ALL 

    SELECT sd.Id, sd.PId, t.RootId 
    FROM temp t 
    INNER JOIN #MyTable sd ON t.Id = sd.PId 
) 

SELECT t2.Id 
FROM temp t 
INNER JOIN temp t2 ON t2.RootId = t.RootId 
WHERE t.Id = @Id 
OPTION (MAXRECURSION 0) 

演示鏈接：http://rextester.com/RAITMT72805