SQL Server 2008 中的 CTE：如何递归计算小计

我有一张表，其中汽车的某些零件按层次结构相关，并且每一行中还有制造这些零件的成本。这是该表的简化：

parentId  Id description qty manufacturingCost costDescripcion
-------- --- ----------- --- ----------------- ---------------
NULL      1  Car          1  100               Assembly the car
NULL      2  Motorcycle   1  100               Assembly the motrocycle
 1       11  Wheel        4   20               Assembly the wheel
11      111  Rim          1   50               Manufacture the rim
11      112  Tire         1   60               Manufacture the tire
 1       12  Door+Window  4   30               Assembly the door and the window
12      121  Door         1   30               Manufacture the door
12      122  Window       2   10               Manufacture the window
 2       11  Wheel        2   15               Assembly the wheel

我需要从“汽车”开始获取整个家谱，并显示每个分支的总数量和总成本。更好的解释是：一辆汽车有 4 个车轮，每个车轮有 1 个轮辋和 1 个轮胎，所以我应该得到 1 个汽车、4 个车轮、4 个轮胎、4 个轮辋。成本有点复杂：组装一辆汽车需要 100 美元，但我必须加上组装 4 个车轮 (4x20) 的成本以及制造 4 个轮辋 (4x50) 和 4 个轮胎的成本(4x60)，门窗也是如此。

这是预期的结果：

parentId  Id description qty manufacturingCost   recLevel
-------- --- ----------- --- -----------------   ---------------
NULL       1  Car          1 940 (100+4*130+4*80) 0
 1        11  Wheel        4 130 (20+50+60)       1
 1        12  Door+Window  4 80  (30+30+2*10)     1
12       121  Door         4 30                   2
12       122  Window       8 10                   2
11       111  Rim          4 50                   2
11       112  Tire         4 60                   2

我可以使用递归函数或存储过程轻松实现这一目标，但对于更复杂的结构来说它非常慢，因此我尝试使用通用表表达式来实现这一点。但我没有找到计算成本的方法。我使用从顶层开始向下的递归 CTE，得到数量总和，但我应该在结构中从内到外对成本进行求和，我该怎么做？

这是创建表的代码：

CREATE TABLE #Costs 
(
  parentId int, 
  Id int, 
  description varchar(50),
  qty int, 
  manufacturingCost int,
  costDescripcion varchar(150)
)

INSERT INTO #Costs VALUES (NULL , 1, 'Car', 1, 100, 'Assembly the car')
INSERT INTO #Costs VALUES (NULL , 2, 'Motorcycle', 1, 100, 'Assembly the motrocycle')
INSERT INTO #Costs VALUES (1 , 11, 'Wheel', 4, 20, 'Assembly the wheel')
INSERT INTO #Costs VALUES (11 , 111, 'Rim', 1, 50, 'Manufacture the rim')
INSERT INTO #Costs VALUES (11 , 112, 'Tire', 1, 60, 'Manufacture the tire')
INSERT INTO #Costs VALUES (1 , 12, 'Door+Window', 4, 30, 'Assembly the door and the window')
INSERT INTO #Costs VALUES (12 , 121, 'Door', 1, 30, 'Manufacture the door')
INSERT INTO #Costs VALUES (12 , 122, 'Window', 2, 10, 'Manufacture the window')
INSERT INTO #Costs VALUES (2 , 11, 'Wheel', 2, 15, 'Assembly the wheel')

这是我写的 CTE：

with CTE(parentId, id, description, totalQty, manufacturingCost, recLevel)
as
(
  select c.parentId, c.id, c.description, c.qty, c.manufacturingCost, 0
  from #Costs c
  where c.id = 1

  union all

  select c.parentId, c.id, c.description, c.qty * ct.totalQty, c.manufacturingCost, ct.recLevel + 1
  from #Costs c
  inner join CTE ct on ct.id = c.parentId 
)
select * from CTE

这是我得到的结果，正如您所看到的，这不是预期的结果（未添加成本）：

parentId  Id description qty manufacturingCost recLevel
-------- --- ----------- --- ----------------- ---------------
NULL       1  Car          1 100                0
 1        11  Wheel        4 20                 1
 1        12  Door+Window  4 30                 1
12       121  Door         4 30                 2
12       122  Window       8 10                 2
11       111  Rim          4 50                 2
11       112  Tire         4 60                 2

使用 CTE 可以做我想做的事吗？如果是这样，我该怎么办？

非常感谢，

Antuan

你可以尝试这样的事情

DECLARE @Table TABLE(
        parentId INT,
        Id INT,
        description VARCHAR(50),
        qty FLOAT,
        manufacturingCost FLOAT,
        costDescripcion VARCHAR(50)
)

INSERT INTO @Table SELECT NULL,1,'Car',1,100,'Assembly the car' 
INSERT INTO @Table SELECT NULL,2,'Motorcycle',1,100,'Assembly the motrocycle' 
INSERT INTO @Table SELECT 1,11,'Wheel',4,20,'Assembly the wheel' 
INSERT INTO @Table SELECT 11,111,'Rim',1,50,'Manufacture the rim' 
INSERT INTO @Table SELECT 11,112,'Tire',1,60,'Manufacture the tire' 
INSERT INTO @Table SELECT 1,12,'Door+Window',4,30,'Assembly the door and the window' 
INSERT INTO @Table SELECT 12,121,'Door',1,30,'Manufacture the door' 
INSERT INTO @Table SELECT 12,122,'Window',2,10,'Manufacture the window' 
INSERT INTO @Table SELECT 2,11,'Wheel',2,15,'Assembly the wheel'

;WITH Vals AS (
        SELECT  *,
                qty Level_Qty,
                CAST(id AS VARCHAR(MAX)) + '\' AS [LEVEL]
        FROM    @Table
        WHERE   parentId IS NULL
        UNION ALL
        SELECT  t.*,                
                p.qty * t.qty Level_Qty,
                CAST(p.[LEVEL] AS VARCHAR(MAX))  + CAST(t.id AS VARCHAR(MAX)) + '\' AS [LEVEL]
        FROM    @Table t INNER JOIN
                Vals p  ON  p.Id = t.parentId
)
SELECT  *,
        (SELECT SUM(Level_Qty * manufacturingCost) FROM Vals WHERE [Level] LIKE v.[LEVEL] + '%') / Level_Qty
FROM    Vals v
ORDER BY [LEVEL]

SQL 小提琴示例 http://www.sqlfiddle.com/#!3/d41d8/4562/0