是否可以創建多對多重繞的可編輯視圖？

Question

考慮以下表：

產品

ID | Name | etc 
1 | Pen | wtv 
2 | Pad | wtv 
3 | Ball | wtv 
...| ... | ... 
thousands of products 

分類

ID | Name | etc 
1 | Office | wtv 
2 | Home | wtv 
3 | Park | wtv 
...| ... | ... 
hundreds of categories 

productCategoryMatrix

ProductID | CategoryID 
1   | 1 
1   | 2 
2   | 1 
2   | 2 
2   | 3 
3   | 3 
... et cetera 

該矩陣允許將多個類別分配給單個產品（典型的多對多關聯）。例如，筆屬於兩類，Office和首頁。我想創建這個數據的可編輯視圖這將是這樣的：

ProductsWithCategories

ProductID | ProductName | Category | Category | Category | Category | Category 
1   | Pen   | 1  | 2  |   |   | 
2   | Pad   | 1  | 2  | 3  |   | 
3   | Ball  | 3  |   |   |   | 
      |    ... Thousands of products ...    | 

注意，如果將產品指定小於5個大類，最後一欄可以保持爲空， 就像在此樣品中。另請注意，業務邏輯規定，單個產品永遠不會超過5個類別，因此只需要5列。

是否可以使用SQL Server 2008 R2創建這種視圖？ 如果您的解決方案也適用於SQL Server 2000，那將是非常棒的，因爲我們只在三週內升級到2008年。如果不是，我們將等待:)

Answer 1

任何視圖都可以使用INSTEAD OF觸發器進行更新。

http://msdn.microsoft.com/en-us/library/ms187956.aspx

在你的情況下，有沒有辦法讓SQL Server自動使它可更新，但你可以在你的觸發映射到行列。

看一看這些頁面：

http://www.sqlteam.com/forums/topic.asp?TOPIC_ID=120679

SQL pivoted table is read-only and cells can't be edited?

視圖可以從這個進行：

DECLARE @Products TABLE (ID INT, Name VARCHAR(50)); 
DECLARE @Categories AS TABLE (ID INT, Name VARCHAR(50)); 
DECLARE @ProductCategoryMatrix AS TABLE (ProductID INT, CategoryID INT); 

INSERT INTO @Products (ID, Name) VALUES (1, 'Pen'), (2, 'Pad'), (3, 'Ball'); 
INSERT INTO @Categories VALUES (1, 'Office'), (2, 'Home'), (3, 'Work'); 
INSERT INTO @ProductCategoryMatrix VALUES (1, 1), (1, 2), (2, 1), (2, 2), (2, 3), (3, 3); 

-- CREATE VIEW AS -- (change variables to real tables) 
WITH CategoriesOrdered AS (
    SELECT p.ID AS ProductID 
      ,'Cat' + CAST(ROW_NUMBER() OVER(PARTITION BY pc.ProductID ORDER BY pc.CategoryID) AS VARCHAR(1)) AS CategoryColumn 
      ,pc.CategoryID 
    FROM @Products p 
    INNER JOIN @ProductCategoryMatrix pc 
     ON pc.ProductID = p.ID 
) 
,CategoriesFlat AS (
    SELECT * 
    FROM CategoriesOrdered 
    PIVOT (MIN(CategoryID) FOR CategoryColumn IN ([Cat1], [Cat2], [Cat3], [Cat4], [Cat5])) AS pvt 
) 
,ProductsWithCategories AS (
    SELECT * 
    FROM @Products p 
    LEFT JOIN CategoriesFlat cf 
     ON cf.ProductID = p.ID 
) 
SELECT * 
FROM ProductsWithCategories; 

這個製作觸發器會涉及相當多的的代碼，但不是非常困難。

Answer 2

這工作完全在SQL 2K，我已經測試

select 
p.ID, 
p.Name, 
c1.cid  as cat1, 
c2.cid  as cat2, 
c3.cid  as cat3, 
c4.cid  as cat4, 
c5.cid  as cat5 
from 
Products p 
inner join     -- use left join if you want to have listed products with any category 
    (select pcm1.ProductID, min(pcm1.CategoryID) as cid 
    from productCategoryMatrix pcm1 group by ProductID) as c1 on p.ID = c1.productID 

left join 
    (select pcm1.productID, min(pcm2.CategoryID) as cid 
    from  productCategoryMatrix pcm1 
    left join productCategoryMatrix pcm2 on pcm1.productID = pcm2.productID and pcm1.CategoryID < pcm2.CategoryID 
    group by pcm1.ProductID 
    ) as c2 on p.ID = c2.productID 

left join 
    (select pcm1.productID, min(pcm3.CategoryID) as cid 
    from  productCategoryMatrix pcm1 
    left join productCategoryMatrix pcm2 on pcm1.productID = pcm2.productID and pcm1.CategoryID < pcm2.CategoryID 
    left join productCategoryMatrix pcm3 on pcm1.productID = pcm3.productID and pcm2.CategoryID < pcm3.CategoryID 
    group by pcm1.ProductID 
    ) as c3 on p.ID = c3.productID 

left join 
    (select pcm1.productID, min(pcm4.CategoryID) as cid 
    from  productCategoryMatrix pcm1 
    left join productCategoryMatrix pcm2 on pcm1.productID = pcm2.productID and pcm1.CategoryID < pcm2.CategoryID 
    left join productCategoryMatrix pcm3 on pcm1.productID = pcm3.productID and pcm2.CategoryID < pcm3.CategoryID 
    left join productCategoryMatrix pcm4 on pcm1.productID = pcm4.productID and pcm3.CategoryID < pcm4.CategoryID 
    group by pcm1.ProductID 
    ) as c4 on p.ID = c4.productID 

left join 
    (select pcm1.productID, min(pcm5.CategoryID) as cid 
    from  productCategoryMatrix pcm1 
    left join productCategoryMatrix pcm2 on pcm1.productID = pcm2.productID and pcm1.CategoryID < pcm2.CategoryID 
    left join productCategoryMatrix pcm3 on pcm1.productID = pcm3.productID and pcm2.CategoryID < pcm3.CategoryID 
    left join productCategoryMatrix pcm4 on pcm1.productID = pcm4.productID and pcm3.CategoryID < pcm4.CategoryID 
    left join productCategoryMatrix pcm5 on pcm1.productID = pcm5.productID and pcm4.CategoryID < pcm5.CategoryID 
    group by pcm1.ProductID 
    ) as c5 on p.ID = c5.productID