选择所有类别中包含的产品

Question

我的Product条记录使用Category表与ProductCategory条记录的多对多相关。

在存储过程中，我有一个包含两个或更多CategoryIds个值的列表（CategoryId）。如何查询Product表并仅返回与CategoryIds中的类别相关的产品？我无法弄清楚我是否需​​要加入或选择或......？

SELECT
  *
FROM 
  Product as P
  -- I can't join here because the relation is many-to-many
WHERE 
  -- This only checks if there is one category to which the product is related
  (SELECT Count(C.CategoryId) FROM ProductCategory as PC INNER JOIN Category as C ON PC.CategoryId = C.CategoryId WHERE PC.ProductId = P.ProductId AND PC.CategoryId IN (@CategoryIds)) > 0

Answer 1

以下语句将返回CSV参数类别中指定的所有产品：

DECLARE @Products TABLE
(
     [ProductID] INT
    ,[ProductName] NVARCHAR(32)
)

DECLARE @Categories TABLE
(
     [CategoryID] INT
    ,[CategotyName] NVARCHAR(32)
)

DECLARE @ProductCategory TABLE
(
    [ProductID] INT
   ,[CategoryID] INT
)


INSERT INTO @Products ( [ProductID], [ProductName])
VALUES (1, 'Product 1')
      ,(2, 'Product 2')
      ,(3, 'Product 3')
      ,(4, 'Product 4')

INSERT INTO @Categories ( [CategoryID], [CategotyName])
VALUES (1, 'Category 1')
      ,(2, 'Category 2')
      ,(3, 'Category 3')

INSERT INTO @ProductCategory ( [ProductID], [CategoryID])
VALUES (1, 1)
      ,(1, 2)
      ,(1, 3)
      ,(2, 1)
      ,(2, 2)
      ,(3, 1)
      ,(4, 2)
      ,(4, 3)

DECLARE @CategoriesCSV NVARCHAR(MAX) = '1,2'


DECLARE @CategoriesXML XML = N'<r><![CDATA[' + REPLACE(@CategoriesCSV, ',', ']]></r><r><![CDATA[') + ']]></r>'

;WITH DataSource AS
(
    SELECT DISTINCT CAST(Tbl.Col.value('.', 'float') AS BIGINT) AS [CategoryID]
    FROM @CategoriesXML.nodes('//r') Tbl(Col)
    WHERE ISNUMERIC(Tbl.Col.value('.', 'varchar(max)')) = 1 
)
SELECT C.[CategoryID]
      ,C.[CategotyName]
      ,P.[ProductID]
      ,P.[ProductName]
FROM @Categories C
INNER JOIN DataSource DS
    ON C.[CategoryID] = DS.[CategoryID]
INNER JOIN @ProductCategory PC
    ON C.[CategoryID] = PC.[CategoryID]
INNER JOIN @Products P
    ON PC.[ProductID] = P.[ProductID] 

上述查询的结果是：