讲解SQL Server 2005数据库表的递归查询

示例如下：

*/

CREATE table CarParts

(

CarID INT NOT NULL,

Part VARCHAR(15),

SubPart VARCHAR(15),

Qty INT

)

GO

INSERT CarParts VALUES (1, 'Body', 'Door', 4)

INSERT CarParts VALUES (1, 'Body', 'Trunk Lid', 1)

INSERT CarParts VALUES (1, 'Body', 'Car Hood', 1)

INSERT CarParts VALUES (1, 'Door', 'Handle', 1)

INSERT CarParts VALUES (1, 'Door', 'Lock', 1)

INSERT CarParts VALUES (1, 'Door', 'Window', 1)

INSERT CarParts VALUES (1, 'Body', 'Rivets', 1000)

INSERT CarParts VALUES (1, 'Door', 'Rivets', 100)

INSERT CarParts VALUES (1, 'Door', 'Mirror', 1)

INSERT CarParts VALUES (1, 'Mirror', 'small_Mirror', 4)

GO

SELECT * FROM CarParts

GO

/*

一辆汽车需要各个零件的数目

1个Body 需要4个Door

1个Door 需要1个Mirror

那么

1个body需要4个Mirror

结构很简单吧

*/

WITH CarPartsCTE(SubPart, Qty)

AS

(

-- 固定成员 (AM):

-- SELECT查询无需参考CarPartsCTE

-- 递归从此处开始

SELECT SubPart, Qty

FROM CarParts

WHERE Part = 'Body'

UNION ALL

-- 递归成员 (RM):

-- SELECT查询参考CarPartsCTE

-- 使用现有数据往下一层展开

SELECT CarParts.SubPart, CarPartsCTE.Qty * CarParts.Qty

FROM CarPartsCTE

INNER JOIN CarParts ON CarPartsCTE.SubPart = CarParts.Part

WHERE CarParts.CarID = 1

)

SELECT SubPart,Qty AS TotalNUM

FROM CarPartsCTE

/*

注意看最下层的small_Mirror 位于 表最后的位置，

由此可以看出改递归不是开始就进行递归查询而是在1层完全展开后在根据该层展开下一层不是深度优先的递归

*/

drop table CarParts

--------------------------------result---------------------------------------

CarID Part SubPart Qty

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

1 Body Door 4

1 Body Trunk Lid 1

1 Body Car Hood 1

1 Door Handle 1

1 Door Lock 1

1 Door Window 1

1 Body Rivets 1000

1 Door Rivets 100

1 Door Mirror 1

1 Mirror small_Mirror 4

(10 row(s) affected)

SubPart TotalNUM

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

Door 4

Trunk Lid 1

Car Hood 1

Rivets 1000

Handle 4

Lock 4

Window 4

Rivets 400

Mirror 4

small_Mirror 16

(10 row(s) affected)

示例：

以下示例显示经理以及向经理报告的雇员的层次列表。

WITH DirectReports(groupid, member, EmployeeLevel,type) AS

(

SELECT groupid, member, 0,type AS EmployeeLevel

FROM groupinfo

WHERE groupid = 'finance_company'

UNION ALL

SELECT e.groupid, e.member, EmployeeLevel + 1,e.type

FROM groupinfo e

INNER JOIN DirectReports d

ON e.groupid = d.member

)

SELECT b.nickname,groupid, member, EmployeeLevel,type

FROM DirectReports,userbasicinfo b

where DirectReports.member=b.id

and type = 1