这是一个有趣的问题。我将用 Hierarchyid 来解决它。首先,设置:
USE tempdb;
IF OBJECT_ID('dbo.Hierarchy') IS NOT NULL
DROP TABLE dbo.[Hierarchy];
CREATE TABLE dbo.Hierarchy
(
ID INT NOT NULL PRIMARY KEY,
ParentID INT NULL,
CONSTRAINT [FK_parent] FOREIGN KEY ([ParentID]) REFERENCES dbo.Hierarchy([ID]),
hid HIERARCHYID,
Amount INT NOT null
);
INSERT INTO [dbo].[Hierarchy]
( [ID], [ParentID], [Amount] )
VALUES
(1, NULL, 100 ),
(2, 1, 50),
(3, 1, 50),
(4, 2, 58),
(5, 2, 7),
(6, 3, 10),
(7, 3, 20)
SELECT * FROM dbo.[Hierarchy] AS [h];
接下来,使用 hiearchyid 的正确值更新 hid 列。我将为此使用沼泽标准递归 cte
WITH cte AS (
SELECT [h].[ID] ,
[h].[ParentID] ,
CAST('/' + CAST(h.[ID] AS VARCHAR(10)) + '/' AS VARCHAR(MAX)) AS [h],
[h].[hid]
FROM [dbo].[Hierarchy] AS [h]
WHERE [h].[ParentID] IS NULL
UNION ALL
SELECT [h].[ID] ,
[h].[ParentID] ,
CAST([c].[h] + CAST(h.[ID] AS VARCHAR(10)) + '/' AS VARCHAR(MAX)) AS [h],
[h].[hid]
FROM [dbo].[Hierarchy] AS [h]
JOIN [cte] AS [c]
ON [h].[ParentID] = [c].[ID]
)
UPDATE [h]
SET hid = [cte].[h]
FROM cte
JOIN dbo.[Hierarchy] AS [h]
ON [h].[ID] = [cte].[ID];
现在繁重的工作已经完成,您想要的结果几乎可以轻松获得:
SELECT p.id, SUM([c].[Amount])
FROM dbo.[Hierarchy] AS [p]
JOIN [dbo].[Hierarchy] AS [c]
ON c.[hid].IsDescendantOf(p.[hid]) = 1
GROUP BY [p].[ID];