CTE错误:"锚点和递归部分之间的类型不匹配"

Question

我正在执行以下声明:

;WITH cte AS (
  SELECT 
    1 as rn, 
    'name1' as nm
  UNION ALL
  SELECT 
    rn + 1,
    nm = 'name' + CAST((rn + 1) as varchar(255))
  FROM cte a WHERE rn < 10)
SELECT * 
FROM cte

...完成错误...

Msg 240, Level 16, State 1, Line 2
Types don't match between the anchor and the recursive part in column "nm" of recursive query "cte".

我在哪里弄错了？

Answer 1

它究竟是什么意思:

'name1' 有不同的数据类型 'name' + CAST((rn+1) as varchar(255))

试试这个(未经测试)

;with cte as
(
select 1 as rn, CAST('name1' as varchar(259)) as nm
union all
select rn+1,nm = 'name' + CAST((rn+1) as varchar(255))
from cte a where rn<10)
select * from cte

基本上,你必须确保长度匹配.对于递归位,CAST('name' AS varchar(4))如果再次失败,则可能必须使用

Answer 2

您需要投射两个nm字段

;with cte as
(
select  1 as rn, 
        CAST('name1' AS VARCHAR(255)) as nm
union all
select  rn+1,
        nm = CAST('name' + CAST((rn+1) as varchar(255)) AS VARCHAR(255))
from cte a where rn<10)
select * from cte

Answer 3

对我来说，问题出在不同的排序规则中。

只有这帮助了我：

;WITH cte AS (
  SELECT 
    1 AS rn, 
    CAST('name1' AS NVARCHAR(4000)) COLLATE DATABASE_DEFAULT AS nm
  UNION ALL
  SELECT 
    rn + 1,
    nm = CAST('name' + CAST((rn + 1) AS NVARCHAR(255)) AS NVARCHAR(4000)) COLLATE DATABASE_DEFAULT
  FROM cte a WHERE rn < 10)
SELECT * 
FROM cte;

希望它可以帮助别人。