如何在sql查询中查找记录的第n个子项

我有一个存储类别和子类别的表（自联接）

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如何在sql查询中查找类别的第N个子项

查找类别

M

的第N个子项（按类别ID排序）：

SELECT ParentCategoryId,
  , CategoryId AS [n-th child]
FROM (
  SELECT CategoryId
    , ParentCategoryId
    , ROW_NUMBER() OVER (PARTITION BY ParentCategoryId ORDER BY CategoryId) as ChildNumber
  FROM Categories
) p
WHERE ChildNumber = %N

select  *
from    (
        select  row_number() over (order by c.CategoryId) as rn
        ,       c.*
        from    Categories p
        join    Categories c
        on      p.CategoryId = c.ParentCategoryId
        where   p.CategoryId = M
        )
where   rn = N

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要查找类别

M

的

N

th子项（按类别ID排序），请执行以下操作：

select  *
from    (
        select  row_number() over (order by c.CategoryId) as rn
        ,       c.*
        from    Categories p
        join    Categories c
        on      p.CategoryId = c.ParentCategoryId
        where   p.CategoryId = M
        )
where   rn = N

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像这样的怎么样

DECLARE @Categories TABLE(
        CategoryId INT, 
        CategoryName VARCHAR(20),
        ParentCategoryId INT
)

INSERT INTO @Categories SELECT 1, '1',NULL
INSERT INTO @Categories SELECT 2, '2',NULL

INSERT INTO @Categories SELECT 3, '1.3',1
INSERT INTO @Categories SELECT 4, '1.4',1

INSERT INTO @Categories SELECT 5, '1.3.5',3
INSERT INTO @Categories SELECT 6, '1.3.6',3
INSERT INTO @Categories SELECT 7, '1.3.6.7',6

INSERT INTO @Categories SELECT 8, '1.4.8',4

DECLARE @CatID INT,
        @NthLevel INT
SELECT  @CatID = 1,
        @NthLevel = 2

;WITH Vals AS (
        SELECT  *,
                1 AS CatLevel
        FROM    @Categories c 
        WHERE   CategoryId IS NULL
        UNION ALL
        SELECT  c.*,
                CatLevel + 1 AS CatLevel
        FROM    Vals v INNER JOIN
                @Categories c   ON  c.ParentCategoryId =  v.CategoryID
)
SELECT  *
FROM    Vals
WHERE   CatLevel = @NthLevel

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这将递归地构建树结构，并将其限制在您要查找的树级别。

类似的内容如何

DECLARE @Categories TABLE(
        CategoryId INT, 
        CategoryName VARCHAR(20),
        ParentCategoryId INT
)

INSERT INTO @Categories SELECT 1, '1',NULL
INSERT INTO @Categories SELECT 2, '2',NULL

INSERT INTO @Categories SELECT 3, '1.3',1
INSERT INTO @Categories SELECT 4, '1.4',1

INSERT INTO @Categories SELECT 5, '1.3.5',3
INSERT INTO @Categories SELECT 6, '1.3.6',3
INSERT INTO @Categories SELECT 7, '1.3.6.7',6

INSERT INTO @Categories SELECT 8, '1.4.8',4

DECLARE @CatID INT,
        @NthLevel INT
SELECT  @CatID = 1,
        @NthLevel = 2

;WITH Vals AS (
        SELECT  *,
                1 AS CatLevel
        FROM    @Categories c 
        WHERE   CategoryId IS NULL
        UNION ALL
        SELECT  c.*,
                CatLevel + 1 AS CatLevel
        FROM    Vals v INNER JOIN
                @Categories c   ON  c.ParentCategoryId =  v.CategoryID
)
SELECT  *
FROM    Vals
WHERE   CatLevel = @NthLevel

---

这将递归地构建树结构，并将其限制在您要查找的树级别。

+1现在问题被编辑为“第n个孩子/孩子”，这个答案更有意义：）+1现在问题被编辑为“第n个孩子/孩子”，这个答案更有意义：）抱歉，这不起作用。我不是在寻找表中的第n个记录，我需要的是一个类别的第n个孩子，我相信它正是这样做的。它为表中的每个ParentCategoryId返回第n个子项。我再次尝试了此操作，但没有成功。它只是ParentId上的分区。无论如何，非常感谢你的帮助。对不起，这没用。我不是在寻找表中的第n个记录，我需要的是一个类别的第n个孩子，我相信它正是这样做的。它为表中的每个ParentCategoryId返回第n个子项。我再次尝试了此操作，但没有成功。它只是ParentId上的分区。无论如何，非常感谢你的帮助