SQL Server 2008中的CTE：如何递归计算小计

Question

我有一张表格，其中汽车的某些部件在层级上存在关联，并且每一行中都有制造这些部件的成本。以下是该表格的简化版：

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

我需要得到以“Car”开始的整个家族谱，显示每个分支的总数量和总成本。更好地解释：一辆汽车有4个轮子，每个轮子有1个轮辋和1个轮胎，因此我应该得到1辆汽车、4个轮子、4个轮胎和4个轮辋。 成本稍微复杂一些：组装一辆汽车的成本为100美元，但我必须加上组装4个车轮的成本（4x20）以及制造4个轮辋（4x50）和4个轮胎（4x60）的成本，门和窗户也是同样的情况。 以下是预期的结果:

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地达到这个目标，但对于更复杂的结构会非常慢，因此我尝试使用公共表达式来完成。但是我没有找到计算成本的方法。我使用一个递归CTE从顶层开始向下，并获得数量的总和，但我应该从内部到外部遍历结构以计算成本，怎么做呢？

这是创建表格的代码：

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')

以下是我写的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，它与预期不符（成本没有被添加）：

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

我可以使用公共表达式（CTE）来实现想要的功能吗？如果可以，如何操作？

非常感谢，

Antuan

- Antuan

Answer 1

您可以尝试这样做：

您可以尝试类似以下的操作

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 Fiddle Example

- Adriaan Stander

---

非常感谢astander，它起作用了！我一直在考虑更改CTE，没有注意到解决方案可以以那种方式查询它。 - Antuan