一个有趣的SQL Server 层级汇总数据问题

IF OBJECT_ID(N‘dbo.MyEmp‘, N‘U‘) IS NOT NULL
BEGIN
    DROP TABLE dbo.MyEmp;
END
GO

CREATE TABLE dbo.MyEmp (
    MyEmpID INT NOT NULL,
    ParentID INT NULL,
    MyEmpName NVARCHAR(20) NOT NULL,
    HoursSalary INT NOT NULL
);
GO

IF OBJECT_ID(N‘PK_U_CL_MyEmp_MyEmpID‘, N‘PK‘) IS NULL
BEGIN
    ALTER TABLE [dbo].[MyEmp] ADD  CONSTRAINT [PK_U_CL_MyEmp_MyEmpID] PRIMARY KEY CLUSTERED 
    (
        [MyEmpID] ASC
    )WITH (PAD_INDEX = OFF, STATISTICS_NORECOMPUTE = OFF, SORT_IN_TEMPDB = OFF, IGNORE_DUP_KEY = OFF, ONLINE = OFF, ALLOW_ROW_LOCKS = ON, ALLOW_PAGE_LOCKS = ON, FILLFACTOR = 90) 
    ON [PRIMARY];
END
GO

IF OBJECT_ID(N‘FK_MyEmp_MyEmp_ParentID‘, N‘F‘) IS NULL
BEGIN
    ALTER TABLE dbo.MyEmp ADD CONSTRAINT FK_MyEmp_MyEmp_ParentID FOREIGN KEY (ParentID) REFERENCES dbo.MyEmp (MyEmpID);
END
GO

-- Insert Test Data
INSERT INTO dbo.MyEmp (MyEmpID, ParentID, MyEmpName, HoursSalary) VALUES  
(1, NULL, N‘Andrew‘, 200),
(2, 1, N‘Nancy‘, 100),
(3, 1, N‘Janet‘, 120),
(4, 3, N‘Michael‘, 80),
(5, 2, N‘Robert‘, 50)
GO

;WITH tData (MyEmpID, MyEmpName, ParentID, ParentName, HoursSalary, ParentHierarchyIndex, HierarchyIndex, LevelID, HierarchyName, HierarchyName2) AS (
    -- 基准点查询
    SELECT MyEmpID                                                                                                /*雇员ID*/
        ,MyEmpName                                                                                                /*雇员名称*/
        ,ISNULL(ParentID, 0) AS ParentID                                                                        /*父雇员ID*/
        ,CAST(N‘‘ AS NVARCHAR(20)) AS ParentName                                                                /*父雇员名称*/
        ,HoursSalary                                                                                            /*小时薪水*/
        ,CAST(CONCAT(‘,‘, ISNULL(ParentID, 0), ‘,‘) AS VARCHAR(300)) AS ParentHierarchyIndex                    /*父层级索引字符串*/
        ,CAST(CONCAT(‘,‘, ISNULL(ParentID, 0), ‘,‘, MyEmpID, ‘,‘) AS VARCHAR(300)) AS HierarchyIndex            /*层级索引字符串串，包含当前层级*/ 
        ,CAST(1 AS INT) AS LevelID                                                                                /*层级ID，根层级为1，层级越深则数字越大*/
        ,CAST(MyEmpName AS NVARCHAR(800)) AS HierarchyName                                                        /*层级名称，树形结构显示*/
        ,CAST(MyEmpName AS NVARCHAR(80)) AS HierarchyName2                                                        /*层级名称2，水平结构显示*/
    FROM dbo.MyEmp
    WHERE ParentID IS NULL
    -- 递归查询
    UNION ALL
    SELECT T.MyEmpID
        ,T.MyEmpName
        ,T.ParentID
        ,T2.MyEmpName
        ,T.HoursSalary
        ,CAST(CONCAT(T2.ParentHierarchyIndex, T.ParentID, ‘,‘) AS VARCHAR(300)) AS ParentHierarchyIndex
        ,CAST(CONCAT(T2.HierarchyIndex, T.MyEmpID, ‘,‘) AS VARCHAR(300)) AS HierarchyIndex 
        ,T2.LevelID + 1 AS LevelID
        ,CAST(CONCAT(REPLICATE(N‘|    ‘, T2.LevelID), T.MyEmpName) AS NVARCHAR(800)) AS HierarchyName
        ,CAST(CONCAT(T2.HierarchyName2, ‘->‘, T.MyEmpName) AS NVARCHAR(80)) AS HierarchyName2
    FROM dbo.MyEmp AS T
        INNER JOIN tData AS T2
            ON T.ParentID = T2.MyEmpID
) 

-- 使用HierarchyIndex来实现

-- CROSS APPLY
SELECT T.*, T2.TotalSalary AS TotalSalary
FROM tData AS T
    CROSS APPLY (SELECT SUM(tData.HoursSalary) AS TotalSalary
    FROM tData
    WHERE HierarchyIndex LIKE CONCAT(T.HierarchyIndex, ‘%‘)) AS T2
ORDER BY T.HierarchyIndex ASC;

-- SELECT + 子查询
--SELECT T.*, TotalSalary = ( SELECT SUM(tData.HoursSalary) FROM tData WHERE tData.HierarchyIndex LIKE CONCAT(T.HierarchyIndex, ‘%‘))
--FROM tData AS T
--ORDER BY T.HierarchyIndex ASC;

-- 使用ParentHierarchyIndex
-- CROSS APPLY
--SELECT T.*, T.HoursSalary + T2.DownMemberTotalHoursSalary AS TotalSalary
--FROM tData AS T
--    CROSS APPLY (
--        SELECT ISNULL(SUM(tData.HoursSalary), 0) AS DownMemberTotalHoursSalary
--        FROM tData
--        WHERE tData.ParentHierarchyIndex LIKE CONCAT(T.ParentHierarchyIndex, T.MyEmpID, ‘%‘)
--    ) AS T2
--ORDER BY T.HierarchyIndex ASC;

-- SELECT + 子查询
--SELECT T.*, T.HoursSalary + (SELECT ISNULL(SUM(tData.HoursSalary), 0) AS DownMemberTotalHoursSalary
--        FROM tData
--        WHERE tData.ParentHierarchyIndex LIKE CONCAT(T.ParentHierarchyIndex, T.MyEmpID, ‘%‘)) AS TotalSalary
--FROM tData AS T
--ORDER BY T.HierarchyIndex ASC;
GO