递归查询字符相加报出类型错误

[luosjz]

如下，报的错误为：类型不匹配之间的锚和递归部分栏“routes”的递归查询“tb” 。
DECLARE @T TABLE (ID INT,start VARCHAR(20),[end] VARCHAR(20))
INSERT INTO @T(ID,start,[end])
SELECT 1,'A','B' UNION ALL
SELECT 2,'B','D' UNION ALL
SELECT 3,'E','F' UNION ALL
SELECT 4,'D','M' UNION ALL
SELECT 5,'B','K' UNION ALL
SELECT 6,'G','W'

;WITH tb AS
(
SELECT
start,
[end],
routes=start+','+[end]
FROM @T WHERE start='B'
UNION ALL
SELECT
A.start,
B.[end],
A.routes+','+B.start
FROM tb AS A
JOIN @T AS B ON A.[end]=B.start
)
SELECT * FROM tb

[liangCK]

DECLARE @T TABLE (ID INT,start VARCHAR(20),[end] VARCHAR(20)) 
INSERT INTO @T(ID,start,[end]) 
SELECT 1,'A','B' UNION ALL 
SELECT 2,'B','D' UNION ALL 
SELECT 3,'E','F' UNION ALL 
SELECT 4,'D','M' UNION ALL 
SELECT 5,'B','K' UNION ALL 
SELECT 6,'G','W' 

;WITH tb AS 
( 
    SELECT 
        start, 
[end], 
routes=CAST(start+','+[end] AS VARCHAR(MAX)) 
    FROM @T WHERE start='B'    
    UNION ALL    
    SELECT 
        A.start, 
B.[end], 
CAST(A.routes+','+B.start AS VARCHAR(MAX)) 
    FROM tb AS A 
        JOIN @T AS B ON A.[end]=B.start 
) 
SELECT * FROM tb

[等不到来世]

DECLARE @T TABLE (ID INT,start VARCHAR(20),[end] VARCHAR(20)) 
INSERT INTO @T(ID,start,[end]) 
SELECT 1,'A','B' UNION ALL 
SELECT 2,'B','D' UNION ALL 
SELECT 3,'E','F' UNION ALL 
SELECT 4,'D','M' UNION ALL 
SELECT 5,'B','K' UNION ALL 
SELECT 6,'G','W' 

;WITH tb AS 
( 
    SELECT 
        start, 
		[end], 
		routes=cast(start+','+[end] as varchar(8000))
    FROM @T WHERE start='B'    
    UNION ALL    
    SELECT 
        A.start, 
B.[end], 
A.routes+','+B.start 
    FROM tb AS A 
        JOIN @T AS B ON A.[end]=B.start 
) 
SELECT * FROM tb

[liangCK]

定位点成员和递归成员的类型需要一致..

所以这里将定位点的routes转换为varchar,而递归成员也转换为varchar

[等不到来世]

with中第一条select的字段长度一定要足够长。