SQL Server递归实例

例子一

-- =============================================
-- 根据EID返回其下属的EID,Layer=1表示直接下属,NULL返回所有下属
-- select EID FROM F_Team_GetSubordinate(2,NULL) -- ============================================= CREATE FUNCTION F_Team_GetSubordinate( @EID INT, @Layer INT) RETURNS @tb TABLE (EID INT,NameCN varchar(50),SupervisorEID INT,Layer INT) AS BEGIN ;WITH CTE AS ( SELECT EID,NameCn,SupervisorEID,0 as Layer FROM TCFG_Employee WHERE EID=@EID UNION ALL SELECT A.EID,A.NameCn,A.SupervisorEID,Layer=layer+1 FROM TCFG_Employee A JOIN CTE B ON A.SupervisorEID = B.EID ) INSERT INTO @tb select EID,NameCN,SupervisorEID,Layer from CTE where (@Layer IS NULL OR Layer=@Layer) return END GO

例子二

--[员工]表含成层级关系
CREATE TABLE Employees (
    empid INT NOT NULL, mgrid INT NULL,--管理者ID字段,用于链接empid empname VARCHAR (25) NOT NULL, salary money NOT NULL, CONSTRAINT PK_Employees PRIMARY KEY (empid), ) GO -- 插入实例数据,允许员工的管理者ID字段为null, INSERT INTO Employees VALUES(1, NULL, 'Nancy', $10000.00) INSERT INTO Employees VALUES(2, 1, 'Andrew', $5000.00) INSERT INTO Employees VALUES(3, 1, 'Janet', $5000.00) INSERT INTO Employees VALUES(4, 1, 'Margaret',$5000.00) INSERT INTO Employees VALUES(5, 2, 'Steven', $2500.00) INSERT INTO Employees VALUES(6, 2, 'Michael', $2500.00) INSERT INTO Employees VALUES(7, 3, 'Robert', $2500.00) INSERT INTO Employees VALUES(8, 3, 'Laura', $2500.00) INSERT INTO Employees VALUES(9, 3, 'Ann', $2500.00) INSERT INTO Employees VALUES(10, 4, 'Ina', $2500.00) INSERT INTO Employees VALUES(11, 7, 'David', $2000.00) INSERT INTO Employees VALUES(12, 7, 'Ron', $2000.00) INSERT INTO Employees VALUES(13, 7, 'Dan', $2000.00) INSERT INTO Employees VALUES(14, 11, 'James', $1500.00) GO --Create Departments table and insert demo values CREATE TABLE Departments ( deptid INT NOT NULL PRIMARY KEY, deptname VARCHAR (25) NOT NULL, deptmgrid INT NULL REFERENCES Employees --部门管理者ID,外键参考Employees的empid字段 ) GO INSERT INTO Departments VALUES (1, 'HR', 2) INSERT INTO Departments VALUES (2, 'Marketing', 7) INSERT INTO Departments VALUES (3, 'Finance', 8) INSERT INTO Departments VALUES (4, 'R&D', 9) INSERT INTO Departments VALUES (5, 'Training', 4) INSERT INTO Departments VALUES (6, 'Gardening', NULL) GO -- 这个自定义函数根据用工ID,返回他所有的下属(包括下属的下属,即所有层) CREATE FUNCTION dbo.fn_getsubtree(@empid AS INT) RETURNS @TREE TABLE ( empid INT NOT NULL, empname VARCHAR(25) NOT NULL, mgrid INT NULL, lvl INT NOT NULL ) AS BEGIN WITH Employees_Subtree(empid, empname, mgrid, lvl) AS --lvl层级字段  ( -- Anchor Member (AM) SELECT empid, empname, mgrid, 0 FROM employees WHERE empid = @empid --这个查询输出将作为下个查询的输入! -- 下属,即那些管理者字段的值等于自己的Employee字段 UNION all -- Recursive Member (RM) SELECT e.empid, e.empname, e.mgrid, es.lvl+1 FROM employees AS e JOIN employees_subtree AS es --employees_subtree是WITH后面的变量名,相当于JOIN自己链接自己 ON e.mgrid = es.empid ) INSERT INTO @TREE SELECT * FROM Employees_Subtree RETURN END GO -- Call for show SELECT * FROM fn_getsubtree(1) --通过这个例子理解CROSS APPLY 说明:表Departments和自定义函数fn_getsubtree链接 --查询每个部门管理者他们包含(所有层次)的下属,特别说明,返回的结果集的记录存在部分记录字段重复 --因为fn_getsubtree是返回所有层次的下属,所以下面的查询也返回每个部门下所有层次的下属 SELECT * FROM Departments AS D CROSS APPLY fn_getsubtree(D.deptmgrid) AS ST --deptmgrid 部门的领导id