145.实现删除指定几点及所有及节点的处理触发器

CREATE TABLE tb(ID int,PID int,Name nvarchar(10))
INSERT tb SELECT 1,NULL,'山东省'
UNION ALL SELECT 2,1   ,'烟台市'
UNION ALL SELECT 4,2   ,'招远市'
UNION ALL SELECT 3,1   ,'青岛市'
UNION ALL SELECT 5,NULL,'四会市'
UNION ALL SELECT 6,5   ,'清远市'
UNION ALL SELECT 7,6   ,'小分市'
GO

--删除处理触发器(同步删除被删除节点的所有子节点)
CREATE TRIGGER tr_DeleteNode ON tb
FOR DELETE
AS
IF @@ROWCOUNT=0 RETURN --如果没有满足删除条件的记录,直接退出
--查找所有被删除节点的子节点
DECLARE @t TABLE(ID int,Level int)
DECLARE @Level int
SET @Level=1
INSERT @t SELECT a.ID,@Level
FROM tb a,deleted d
WHERE a.PID=d.ID
WHILE @@ROWCOUNT>0
BEGIN
	SET @Level=@Level+1
	INSERT @t SELECT a.ID,@Level
	FROM tb a,@t b
	WHERE a.PID=b.ID
		AND b.Level=@Level-1
END
DELETE a
FROM tb a,@t b
WHERE a.ID=b.ID
GO

--删除
DELETE FROM tb WHERE ID in(2,3,5)
SELECT * FROM tb
/*--结果
ID          PID        Name 
---------------- ----------------- ---------- 
1           NULL      山东省
--*/