0

我有这个查询应该为相关类别建立层次结构路径

;with cte as 
(

    select 
        CAST(1 as int)  as RelationID,
        1 CategoryID,
        c.Name Name
        ,CAST(('') as varchar(1000)) as Indent,CAST(c.Name as varchar(1000)) as Pathway,0 as Level 
    from
        Categories c
    where 
        c.ID = 1

    union all

    select
        relation.RelationID,
        relation.CategoryID,
        c.Name Name
       ,CAST(('|— ' + cte.Indent) as varchar(1000)) as Indent,CAST((cte.Pathway + '/' + c.Name) as varchar(1000)) as Pathway,cte.Level + 1 as Level
    from
        Category_Relations relation
    inner join
        Categories c on c.Id = relation.CategoryID
    inner join cte on cte.RelationID = relation.RelationID
    where c.ID > 1
)
select * from cte

现在我想知道为什么它会无限！

我这样有两张桌子：

Categories:
ID,Name
1,Main
2,Cat1
3,Cat2
4,Cat3
5,Cat4
6,Cat1.1
7,Cat1.2
8,Cat2.1
9,Cat3.1

Category_Relations:
ID,RelationID,CategoryID
1,0,1 (main cat)
2,1,2
3,1,3
4,1,4
5,1,5
6,2,6
7,2,7
8,3,8
9,4,9

理想情况下，SQL 应该构建路径：

main
main/cat1
main/cat2
main/cat3
main/cat4
main/cat1/cat1.1
main/cat1/cat1.2
main/cat2/cat2.1
main/cat3/cat3.1

但它会无限并给出递归错误，对此有什么帮助吗？

4

1 回答 1

0

我才意识到我犯了一个错误，

如果您仔细检查以下几行，则会出现错误：

select
    relation.RelationID

问题是它RelationID永远不会改变（感谢HABO）所以我不得不稍微调整一下并替换relation.RelationID为relation.ID它总是必须是独一无二的。

问题解决了！

于 2013-11-03T15:59:48.593 回答