1 SET STATISTICS IO ON;
2 SET STATISTICS TIME ON;
3 GO
4 IF OBJECT_ID(N'dbo.t1') IS NOT NULL
5 DROP TABLE dbo.t1;
6 GO
7 CREATE TABLE t1
8 (
9 id INT IDENTITY(1, 1)
10 PRIMARY KEY ,
11 a NVARCHAR(2) ,
12 b NVARCHAR(2)
13 );
14 --建立索引a
15 CREATE NONCLUSTERED INDEX [NonClusteredIndex-20190507-201219] ON [dbo].[t1]
16 (
17 [a] ASC
18 )
19 INCLUDE ( [b]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY];
20 GO
21 --建立索引b
22 CREATE NONCLUSTERED INDEX [NonClusteredIndex-20190507-201235] ON [dbo].[t1]
23 (
24 [b] ASC
25 )
26 INCLUDE ( [a]) WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, DROP_EXISTING = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON) ON [PRIMARY];
27 GO
28
29
30
31
32
33 WITH cte_0 ( a, b )
34 AS ( SELECT 1 ,
35 2
36 UNION ALL
37 SELECT 1 ,
38 3
39 UNION ALL
40 SELECT 2 ,
41 4
42 UNION ALL
43 SELECT 2 ,
44 5
45 UNION ALL
46 SELECT 2 ,
47 3
48 UNION ALL
49 SELECT 3 ,
50 6
51 UNION ALL
52 SELECT 4 ,
53 9
54 UNION ALL
55 SELECT 5 ,
56 7
57 UNION ALL
58 SELECT 6 ,
59 9
60 UNION ALL
61 SELECT 7 ,
62 8
63 UNION ALL
64 SELECT 8 ,
65 10
66 UNION ALL
67 SELECT 9 ,
68 10
69 UNION ALL
70 SELECT 9 ,
71 12
72 UNION ALL
73 SELECT 10 ,
74 11
75 UNION ALL
76 SELECT 11 ,
77 12
78 )
79 INSERT INTO t1
80 ( a ,
81 b
82 )
83 SELECT a ,
84 b
85 FROM cte_0
86 UNION ALL
87 SELECT b ,
88 a
89 FROM cte_0;
90 --加上是否循环的标记（效率较不加循环标记要高）
91 WITH cte_a
92 AS ( SELECT a ,
93 b
94 FROM dbo.t1
95 --UNION ALL
96 --SELECT b ,
97 -- a
98 --FROM dbo.t1
99 ),
100 cte_b
101 AS ( SELECT a ,
102 b ,
103 0 AS isok ,
104 CAST(a + '>' + b AS NVARCHAR(MAX)) AS c_path ,
105 1 AS nlevel
106 FROM cte_a
107 WHERE a = '4'--起点
108 UNION ALL
109 SELECT s.a ,
110 s.b ,
111 CASE WHEN s.b = '11' THEN 1--如果下一层找到了终点，那么不需要继续向下找
112 ELSE 0
113 END AS isok ,
114 CAST(p.c_path + '>' + s.b AS NVARCHAR(MAX)) AS c_path ,
115 p.nlevel + 1
116 FROM cte_a AS s
117 INNER JOIN cte_b AS p ON p.b = s.a
118 WHERE CHARINDEX(s.b, p.c_path) = 0
119 AND p.isok = 0
120 ),
121 cte_c
122 AS ( SELECT *
123 FROM cte_b
124 --WHERE b = '11'--终点
125 )
126 SELECT *
127 FROM cte_c
128 --WHERE cte_c.nlevel = ( SELECT MIN(cte_c.nlevel)
129 -- FROM cte_c
130 -- );
像个乞丐
