我们经常遇到树型结构，把它们显示在一个类似TreeView控件上的情况。这时我们可以使用Recursive Common Table Expressions(CTE)实现 。
下面是一个简单的Family Tree 示例：
- 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:
希望对您有帮助
