X 次递归循环后停止查询

Question

我有一个递归查询。该查询在大多数情况下仅在存在无限循环时才有效我想从数据库而不是

获取一些结果

The maximum recursion 100 has been exhausted before statement completion.

查询如下：

WITH bom ( [id],[parentNumber],[warehouse],[sequenceNumber] 
                    ,[childNumber],[childDescription],[qtyRequired],[childItemClass] 
                    ,[childItemType],[scrapFactor],[bubbleNumber] ,[operationNumber] 
                    ,[effectivityDate],[discontinuityDate],[companyID]) AS (
                    select * from [products].[BillOfMaterial] where parentNumber IN ('XXXXXXXXXX')
                     and companyID = '0'UNION ALL 
                    select c.* from bom b INNER JOIN [products].[BillOfMaterial] c on b.childNumber = c.parentNumber  and c.companyID = '0')
                     SELECT distinct * FROM bom

所以我想更改查询，以便我可以解决上面的问题并返回某些级别的数据。通常这棵树不会超过 5 层。

这在 Sql 服务器递归查询中是否可行？

Answer 1

我不认为有一个 OPTION 可以做你想做的事，但你可以创建一个变量来保存你希望递归发生的最大次数，并在查询：

Declare @MaxLevel Int = 5;

With bom (id, parentNumber, warehouse, sequenceNumber, childNumber, childDescription, qtyRequired, childItemClass, childItemType, scrapFactor, bubbleNumber,
          operationNumber, effectivityDate, discontinuityDate, companyID, Level
         )
As (Select *,
           1 As Level
    From   products.BillOfMaterial
    Where  parentNumber In ( 'XXXXXXXXXX' )
           And companyID = '0'
    Union All
    Select c.*,
           Level + 1 As Level
    From   bom b
    Inner Join products.BillOfMaterial c
        On b.childNumber = c.parentNumber
           And c.companyID = '0'
    Where  Level < @MaxLevel
   )
Select Distinct *
From   bom;

这是一个带日期的工作示例：

Declare @MaxLevel Int = 5;

;With Cte As
(
    Select  Convert(Date, GetDate()) As Date,
            1 As Level
    Union All
    Select  DateAdd(Day, 1, Date) As Date,
            Level + 1 As Level
    From    Cte
    Where   Level < @MaxLevel
)
Select  *
From    Cte

Results

Date        Level
2017-09-14  1
2017-09-15  2
2017-09-16  3
2017-09-17  4
2017-09-18  5

Answer 2

像下面这样的事情应该做：

WITH bom ( [id],[parentNumber],[warehouse],[sequenceNumber] 
                    ,[childNumber],[childDescription],[qtyRequired],[childItemClass] 
                    ,[childItemType],[scrapFactor],[bubbleNumber] ,[operationNumber] 
                    ,[effectivityDate],[discontinuityDate],[companyID])
 AS (
    select *, 1 as Depth
     from [products].[BillOfMaterial]
     where parentNumber IN ('XXXXXXXXXX')
      and companyID = '0'
    union all select c.*, b.Depth + 1 as Depth
     from bom b
      INNER JOIN [products].[BillOfMaterial] c
       on b.childNumber = c.parentNumber
        and c.companyID = '0'
     --where b.Depth < xx
    )
 SELECT distinct * FROM bom
  --where Depth < xx

我没有测试过这个精确的代码，我不确定应该使用哪个 where 子句，但我以前做过这样的查询。这个想法是在跟踪深度 xx 中放置一个任意计数器，并在达到该深度时切断查询。

X 次递归循环后停止查询

Stop query after X recursive loops

sql-server

recursive-query