CTE error: “Types don't match between the anch

问题:

I am executing the following statement:

;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

...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".

Where am I making the mistake?

回答1:

Exactly what it says:

'name1' has a different data type to 'name' + CAST((rn+1) as varchar(255))

Try this (untested)

;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

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

回答2:

You need to cast both nm fields

;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

回答3:

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

回答4:

For me problem was in different collation.

Only this helped me:

;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;

Hope it can help someone else.

回答5:

;with tmp1(NewsId,DataItem ,HeaderText)
 as
  (

    select NewsId, LEFT(HeaderText, CHARINDEX(',',HeaderText+',')-1),
    STUFF(HeaderText, 1, CHARINDEX(',',HeaderText+','), '') 
    from Currentnews

    union all

    select NewsId, LEFT(HeaderText, CHARINDEX(',',HeaderText+',')-1),
    STUFF(HeaderText, 1, CHARINDEX(',',HeaderText+','), '')
    from tmp1
    where HeaderText > ''

   )

   select NewsId, DataItem
   from tmp1
   order by NewsId