CTE 错误:“锚点和递归部分之间的类型不匹配"；

问题描述

我正在执行以下语句:

;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

...以错误结束...

...which finishes with the error...

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".

我哪里出错了?

推荐答案

正是它所说的:

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

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

Basically, you have to ensure the length matches too. For the recursive bit, you may have to use CAST('name' AS varchar(4)) if it fails again

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