在特定條件下打破的CTE SQL查詢

Question

我有以下SQL Server CTE查詢：

;with x 
as (
    select childref, 0 as lvl 
    from [dbo].[TOMatriX] 
    where parentref = @parentref 

    union all 

    select m.childref, x.lvl+1 
    from [dbo].[TOMatriX] m 
    inner join x on m.parentref = x.childref 
) 
select 
    lvl [Level], 
count(*) [Count], 
    stuff((select ', ' + CAST(ChildRef AS CHAR(9)) 
      from x t2 where t1.lvl = t2.lvl 
      for xml path('')), 
      1,2,'') [Members] 
from x t1 
group by lvl 

我需要水平的細節高達12只，所以我上面的查詢修改爲：

;with x 
as (
    select childref, 0 as lvl 
    from [dbo].[TOMatriX] 
    where parentref = @parentref 

    union all 

    select m.childref, x.lvl+1 
    from [dbo].[TOMatriX] m 
    inner join x on m.parentref = x.childref 
) 
select top 12 
    lvl [Level], 
count(*) [Count], 
    stuff((select ', ' + CAST(ChildRef AS CHAR(9)) 
      from x t2 where t1.lvl = t2.lvl 
      for xml path('')), 
      1,2,'') [Members] 
from x t1 
group by lvl 

但我怎麼可以使用OPTION（MAXRECURSION）上破12級這個遞歸，我不能夠使用MAXRECURSION選項我的查詢中，我曾嘗試如下使用它：

;with x 
as (
    select childref, 0 as lvl 
    from [dbo].[TOMatriX] 
    where parentref = 100000001 

    union all 

    select m.childref, x.lvl+1 
    from [dbo].[TOMatriX] m 
    inner join x on m.parentref = x.childref 
) 
select 
    lvl [Level], 
count(*) [Count], 
    stuff((select ', ' + CAST(ChildRef AS CHAR(9)) 
      from x t2 where t1.lvl = t2.lvl 
      for xml path('')), 
      1,2,'') [Members] 
from x t1 
group by lvl 
OPTION (MAXRECURSION 12); 

但我得到以下錯誤：

聲明終止。報表完成前，最大遞歸12已用盡。

那麼，如何使用OPTION（maxrecursion）來停止12級的遞歸，就像在第二個查詢中使用TOP一樣。

注：表的結構法

TABLE [dbo].[TOMatriX](

     [ParentRef] [int] NOT NULL, 
     [ChildRef] [int] NOT NULL, 
-- Some Other Columns as well ... 

) 

如果可能的話，請諮詢任何性能改進爲好。

Answer 1

這裏是你如何把一個限制條件的一個例子：

with x as (
     select childref, 0 as lvl 
     from [dbo].[TOMatriX] 
     where parentref = 100000001 
     union all 
     select m.childref, x.lvl+1 
     from [dbo].[TOMatriX] m inner join 
      x 
      on m.parentref = x.childref 
     where x.lvl <= 12 
    )