你需要的是一个递归查询。
这个微软Technet的例子正好符合你的要求,尽管在这个例子中,我们是针对员工层次结构而不是文件夹进行操作。
从链接页面中可以看到:
CREATE TABLE dbo.MyEmployees
(
EmployeeID smallint NOT NULL,
FirstName nvarchar(30) NOT NULL,
LastName nvarchar(40) NOT NULL,
Title nvarchar(50) NOT NULL,
DeptID smallint NOT NULL,
ManagerID int NULL,
CONSTRAINT PK_EmployeeID PRIMARY KEY CLUSTERED (EmployeeID ASC)
);
INSERT INTO dbo.MyEmployees VALUES
(1, N'Ken', N'Sánchez', N'Chief Executive Officer',16,NULL)
,(273, N'Brian', N'Welcker', N'Vice President of Sales',3,1)
,(274, N'Stephen', N'Jiang', N'North American Sales Manager',3,273)
,(275, N'Michael', N'Blythe', N'Sales Representative',3,274)
,(276, N'Linda', N'Mitchell', N'Sales Representative',3,274)
,(285, N'Syed', N'Abbas', N'Pacific Sales Manager',3,273)
,(286, N'Lynn', N'Tsoflias', N'Sales Representative',3,285)
,(16, N'David',N'Bradley', N'Marketing Manager', 4, 273)
,(23, N'Mary', N'Gibson', N'Marketing Specialist', 4, 16);
然后
WITH DirectReports (ManagerID, EmployeeID, Title, DeptID, Level)
AS
(
SELECT e.ManagerID, e.EmployeeID, e.Title, edh.DepartmentID,
0 AS Level
FROM dbo.MyEmployees AS e
INNER JOIN HumanResources.EmployeeDepartmentHistory AS edh
ON e.EmployeeID = edh.BusinessEntityID AND edh.EndDate IS NULL
WHERE ManagerID IS NULL
UNION ALL
SELECT e.ManagerID, e.EmployeeID, e.Title, edh.DepartmentID,
Level + 1
FROM dbo.MyEmployees AS e
INNER JOIN HumanResources.EmployeeDepartmentHistory AS edh
ON e.EmployeeID = edh.BusinessEntityID AND edh.EndDate IS NULL
INNER JOIN DirectReports AS d
ON e.ManagerID = d.EmployeeID
)
SELECT ManagerID, EmployeeID, Title, DeptID, Level
FROM DirectReports
INNER JOIN HumanResources.Department AS dp
ON DirectReports.DeptID = dp.DepartmentID
WHERE dp.GroupName = N'Sales and Marketing' OR Level = 0;
GO
你的结果是
ManagerID EmployeeID Title Level
--------- ---------- ----------------------------- ------
NULL 1 Chief Executive Officer 0
1 273 Vice President of Sales 1
273 16 Marketing Manager 2
273 274 North American Sales Manager 2
273 285 Pacific Sales Manager 2
16 23 Marketing Specialist 3
274 275 Sales Representative 3
274 276 Sales Representative 3
285 286 Sales Representative 3