我們經常遇到樹型結構，把它們顯示在一個類似TreeView控件上的情況。這時我們可以使用Recursive Common Table expressions(CTE)實現
下面是一個簡單的Family Tree 示例：
代碼如下:
DECLARE @TT TABLE (ID int,Relation varchar(25),Name varchar(25),ParentID int)
INSERT @TT SELECT 1,’ Great GrandFather’ , ‘Thomas Bishop’, null UNION ALL
SELECT 2,’Grand Mom’, ‘Elian Thomas Wilson’ , 1 UNION ALL
SELECT 3, ‘Dad’, ‘James Wilson’,2 UNION ALL
SELECT 4, ‘Uncle’, ‘Michael Wilson’, 2 UNION ALL
SELECT 5, ‘Aunt’, ‘Nancy Manor’, 2 UNION ALL
SELECT 6, ‘Grand Uncle’, ‘Michael Bishop’, 1 UNION ALL
SELECT 7, ‘Brother’, ‘David James Wilson’,3 UNION ALL
SELECT 8, ‘Sister’, ‘Michelle Clark’, 3 UNION ALL
SELECT 9, ‘Brother’, ‘Robert James Wilson’, 3 UNION ALL
SELECT 10, ‘Me’, ‘Steve James Wilson’, 3
———-Query—————————————
;WITH FamilyTree
AS(
SELECT *, CAST(NULL AS VARCHAR(25)) AS ParentName, 0 AS Generation FROM @TT
WHERE ParentID IS NULL
UNION ALL
SELECT Fam.*,FamilyTree.Name AS ParentName, Generation + 1 FROM @TT AS Fam
INNER JOIN FamilyTree ON Fam.ParentID = FamilyTree.ID
)SELECT * FROM FamilyTree
Output:
希望對您有幫助
Author: Petter Liu
