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  • SQL递归调用层级示例

    View Code
    --调用方法:
    --
    select * from GetChild('24')
    --
    select id from GetChild('24')
    --
    select * from KuCun where ProductType in(select id from GetChild('24'))

    CREATE FUNCTION [dbo].[GetChild] ( @ID VARCHAR(10) )
    RETURNS @t TABLE
    (
    ID VARCHAR(10) ,
    ParentID VARCHAR(10) ,
    Level INT
    )
    AS
    BEGIN
    DECLARE @i INT
    SET @i = 1
    INSERT INTO @t
    SELECT @ID, @ID, 0 --当前级,本级,如果不要的话可以注释掉或再加个参数来选择操作
    INSERT INTO @t
    SELECT ID, ParentID, @i
    FROM Dept
    WHERE ParentID = @ID

    WHILE @@rowcount <> 0
    BEGIN
    SET @i = @i + 1
    INSERT INTO @t
    SELECT a.ID, a.ParentID, @i
    FROM Dept a ,
    @t b
    WHERE a.ParentID = b.ID
    AND b.Level = @i - 1
    END
    RETURN
    END

    --------------------------------------------------------------------------------
    --
    在SQL Server2005中其实提供了CTE[公共表表达式]来实现递归:
    DECLARE @Id INT
    SET @Id = 24 ;
    ---在此修改父节点

    WITH RootNodeCTE ( Id, ParentId )
    AS ( SELECT Id, ParentId
    FROM Dept
    WHERE ParentId IN ( @Id )
    UNION ALL
    SELECT Dept.Id, Dept.ParentId
    FROM RootNodeCTE
    INNER JOIN Dept ON RootNodeCTE.Id = Dept.ParentId
    )
    SELECT *
    FROM RootNodeCTE

    --------------------------------------------------------------------------------
    --
    ------------------------------------------------------------------------------
    --
    ------------------------------------------------------------------------------

    --生成测试数据
    CREATE TABLE Dept
    (
    ID INT ,
    ParentID INT ,
    msg VARCHAR(20)
    )
    INSERT INTO Dept
    SELECT 1, 0, NULL
    INSERT INTO Dept
    SELECT 2, 1, NULL
    INSERT INTO Dept
    SELECT 3, 1, NULL
    INSERT INTO Dept
    SELECT 4, 2, NULL
    INSERT INTO Dept
    SELECT 5, 3, NULL
    INSERT INTO Dept
    SELECT 6, 5, NULL
    INSERT INTO Dept
    SELECT 7, 6, NULL
    go


    --创建用户定义函数
    CREATE FUNCTION [dbo].[GetChild] ( @ID VARCHAR(10) )
    RETURNS @t TABLE
    (
    ID VARCHAR(10) ,
    ParentID VARCHAR(10) ,
    Level INT
    )
    AS
    BEGIN
    DECLARE @i INT
    SET @i = 1
    INSERT INTO @t
    SELECT @ID, @ID, 0 --当前级,本级,如果不要的话可以注释掉或再加个参数来选择操作
    INSERT INTO @t
    SELECT ID, ParentID, @i
    FROM Dept
    WHERE ParentID = @ID

    WHILE @@rowcount <> 0
    BEGIN
    SET @i = @i + 1
    INSERT INTO @t
    SELECT a.ID, a.ParentID, @i
    FROM Dept a ,
    @t b
    WHERE a.ParentID = b.ID
    AND b.Level = @i - 1
    END
    RETURN
    END


    --执行查询
    SELECT ID
    FROM dbo.GetChild(3)
    go

    --输出结果
    /*

    3
    5
    6
    7
    */

    --删除测试数据
    DROP FUNCTION GetChild
    DROP TABLE Dept


     

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  • 原文地址:https://www.cnblogs.com/ToddLai/p/2287388.html
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