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sql - 使用递归查询的存储过程

问题描述

我正在编写一个存储过程，它应该返回结果，并且相同的结果将作为输入传递给存储过程，并且在任何特定时间输入和输出相同后递归应该停止。

下面是存储过程/函数和运行命令（存储过程的新功能）。

CREATE FUNCTION dbo.Ancestors (@List VARCHAR(MAX))
RETURNS TABLE
AS
RETURN
WITH CTE AS
(
 SELECT DISTINCT Child AS RESULT FROM example WHERE Parent IN( SELECT Id = 
 Item FROM dbo.SplitInts(@List, ',')) or child IN (SELECT Id = Item FROM 
 dbo.SplitInts(@List, ','))
 UNION ALL
 SELECT DISTINCT Parent AS RESULT FROM example WHERE Parent IN( SELECT Id = 
 Item FROM dbo.SplitInts(@List, ',')) or child IN (SELECT Id = Item FROM 
 dbo.SplitInts(@List, ','))
 )
SELECT RESULT FROM CTE
UNION
SELECT RESULT FROM CTE
GO

CREATE PROCEDURE GetAncestors (@thingID VARCHAR(MAX))
AS
SELECT RESULT FROM dbo.Ancestors(@thingID)
GO

EXEC GetAncestors @thingID = '100'

结果是 - '100,101'

EXEC GetAncestors @thingID = '100,101'

结果是 - '100,101,102'

EXEC GetAncestors @thingID = '100,101,102'

结果是 - '100,101,102'

我实际上正在寻找的是通过传递 100 或 101 或 102 一次性给出结果

结果应该是 - '100,101,102'

下面是示例表：

|     Parent          |     Child        |
|---------------------|------------------|
|      100            |      101         |
|---------------------|------------------|
|      101            |      102         |
|---------------------|------------------|

标签： sqlsql-serverstored-proceduressql-server-2005

解决方案

看起来您需要一个简单的递归查询，从给定节点开始向下遍历树。CTE返回一个 pair 列表，所以我将(Parent, Child)它们联合在一起以获得单个节点的列表（并在此过程中删除重复项）。

请注意，查询是递归的。CTE（公用表表达式）引用自身。

样本数据

我添加了几行以实际查看发生了什么。

DECLARE @T TABLE (Parent int, Child int);

INSERT INTO @T VALUES
(100, 101),
(101, 102),
(102, 103),
(103, 104),
(101, 108),
(108, 109),
(208, 209),
(209, 210);

询问

WITH
CTE
AS
(
    SELECT
        Parent, Child
    FROM @T
    WHERE Parent = 100

    UNION ALL

    SELECT
        T.Parent, T.Child
    FROM
        CTE
        INNER JOIN @T AS T ON T.Parent = CTE.Child
)
SELECT
    Parent AS Result
FROM CTE

UNION

SELECT
    Child AS Result
FROM CTE
;

结果

Result
100
101
102
103
104
108
109

您可以将查询放在存储过程中，如下所示：

CREATE PROCEDURE GetAncestors(@thingID int)
AS
BEGIN
    SET NOCOUNT ON;

    WITH
    CTE
    AS
    (
        SELECT
            Example.Parent, Example.Child
        FROM Example
        WHERE Parent = @thingID

        UNION ALL

        SELECT
            Example.Parent, Example.Child
        FROM
            CTE
            INNER JOIN Example ON Example.Parent = CTE.Child
    )
    SELECT
        Parent AS Result
    FROM CTE

    UNION

    SELECT
        Child AS Result
    FROM CTE
    ;

END
GO

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