如何获取最末级的数据

[小野马1209]

--如何查最末级的代码
DECLARE @t table (ID varchar(20),Leval int,ParentId varchar(20))
INSERT INTO @t
SELECT 'A',1,'' UNION ALL
SELECT 'A01',2,'A' UNION ALL
SELECT 'A01',3,'A01' UNION ALL
SELECT 'B01',2,'A' 

SELECT * FROM @t
/*
想要的结果
A01	3	A01
B01	2	A
*/

[小野马1209]

案例更新了下

DECLARE @t table (ID varchar(20),Leval int,ParentId varchar(20))
INSERT INTO @t
SELECT 'A',1,'' UNION ALL
SELECT 'A01',2,'A' UNION ALL
SELECT 'A0101',3,'A01' UNION ALL
SELECT 'B01',2,'A' 

SELECT * FROM @t
/*
想要的结果
A0101	3	A01
B01	2	A
*/

[听雨停了]

引用 1 楼 kaijie_wu1209 的回复:

DECLARE @t table (ID varchar(20),Leval int,ParentId varchar(20))
INSERT INTO @t
SELECT 'A',1,'' UNION ALL
SELECT 'A01',2,'A' UNION ALL
SELECT 'A0101',3,'A01' UNION ALL
SELECT 'B01',2,'A' 

SELECT a.* FROM @t a
left JOIN @t b ON a.id=b.ParentId
WHERE isnull(b.id,'')='' 

/*
ID                   Leval       ParentId
-------------------- ----------- --------------------
A0101                3           A01
B01                  2           A
*/

[二月十六]

不是父节点就应该是最末级

DECLARE @t table (ID varchar(20),Leval int,ParentId varchar(20))
INSERT INTO @t
SELECT 'A',1,'' UNION ALL
SELECT 'A01',2,'A' UNION ALL
SELECT 'A0101',3,'A01' UNION ALL
SELECT 'B01',2,'A' 
 
SELECT  *
FROM    @t
WHERE   ID NOT IN ( SELECT  ParentId
                    FROM    @t )