查找担保圈-step1-担保圈表函数

 USE [test];
 GO
 /****** Object:  UserDefinedFunction [dbo].[f_findrecycle]    Script Date: 2019/7/8 14:37:08 ******/
 SET ANSI_NULLS ON;
 GO
 SET QUOTED_IDENTIFIER ON;
 GO
 ALTER FUNCTION [dbo].[f_findrecycle]
 (
     @cname NVARCHAR(100), --起点
     @nlevel INT           --递归的层数
 )
 RETURNS TABLE
 AS
 RETURN
 (
     WITH cte_A (kmmc, bzrmc, isrecycle, full_path, nlevel)
     AS (SELECT [KHMC],
                [BZRMC],
                0 AS isrecycle,
                CAST(KHMC + '<' + BZRMC AS NVARCHAR(MAX)) AS full_path,
                1 AS nlevel
         FROM [dbo].[dbgx]
         WHERE KHMC = @cname
         UNION ALL
         SELECT s.KHMC,
                s.BZRMC,
                CASE
                    WHEN s.BZRMC = @cname THEN
                        1 --如果下层找到了起点，就停止递归
                    ELSE
                        0
                END AS isrecycle,
                CAST(p.full_path + '<' + s.BZRMC AS NVARCHAR(MAX)) AS full_path,
                p.nlevel + 1 AS nlevel
         FROM [dbo].[dbgx] AS s
             INNER JOIN cte_A AS p
                 ON s.KHMC = p.bzrmc
         WHERE CHARINDEX(s.BZRMC, p.full_path) IN ( 0, 1 ) --防止找到起点（担保圈）后继续进行递归查找
               AND p.isrecycle = 0 --上层没有找到起点，继续递归
               AND p.nlevel <= @nlevel --递归的层数
     )
     SELECT a.kmmc,
            a.bzrmc,
            a.isrecycle,
            a.full_path,
            a.nlevel
     FROM cte_A AS a
     WHERE a.isrecycle = 1
 );