8.2.5 校验插入指定结点是否导致编码循环的示例函数.sql

sqlserver 数据库编程的绝好脚本

CREATE FUNCTION f_CheckCode(
@ID char(3),  --要插入的节点编码
@PID char(3)  --要插入的节点的上级编码
)RETURNS bit
AS
BEGIN
	DECLARE @t TABLE(ID char(3),Level int,Flag tinyint)
	DECLARE @level int
	SET @level=0
	INSERT @t SELECT ID,@level,CASE WHEN ID=@PID THEN 1 ELSE 0 END
	FROM tb
	WHERE PID=@ID
	WHILE @@ROWCOUNT>0 
		AND NOT EXISTS(SELECT * FROM @t WHERE Flag=1)
	BEGIN
		SET @level=@level+1
		INSERT @t SELECT ID,@level,CASE WHEN ID=@PID THEN 1 ELSE 0 END
		FROM tb a,@t b
		WHERE a.PID=b.ID
			AND b.Level=@level-1
	END
	RETURN((SELECT MAX(Flag) FROM @t))
END