ROW_NUMBER 为所有行返回相同的值（+ 查询性能）

Question

我有以下查询（用于展示问题）

WITH
    CategoryPromotions
    AS
    (
        SELECT CategoryId = 7, Price = 10
             UNION ALL
        SELECT CategoryId = 3, Price = 15
             UNION ALL
        SELECT CategoryId = 1, Price = 5
    )
,
       Products
       AS
       (
             SELECT Id = 1, Price = 20
       )
,
       ProductsCategories
       AS
       (
             SELECT ProductId = 1, CategoryId = 2
             UNION ALL
             SELECT ProductId = 1, CategoryId = 8
             UNION ALL
             SELECT ProductId = 1, CategoryId = 6
       )
,
       Tally
       AS
       (
             SELECT N = 1
             UNION ALL
             SELECT N = 2
             UNION ALL
             SELECT N = 3
             UNION ALL
             SELECT N = 4
             UNION ALL
             SELECT N = 5
       )
,
       Hierarchy
       AS
       (
             SELECT Id = 2, SortPath = 0x00000001000000070000000400000002
             UNION ALL
             SELECT Id = 8, SortPath = 0x00000001000000070000000400000008
             UNION ALL
             SELECT Id = 6, SortPath = 0x0000000300000006
       )
SELECT ProductsCategories.*, xD.*
FROM Products
       RIGHT JOIN ProductsCategories
             ON Products.Id = ProductsCategories.ProductId
       CROSS APPLY
       (
             SELECT TOP (1) promos.CategoryId
                    , Products.Price AS BasePrice
                    , promos.Price
                    , (
                        CASE
                            WHEN promos.Price IS NOT NULL THEN
                                (Products.Price - promos.Price)
                            ELSE
                                Products.Price
                        END
                    ) AS DiscountedPrice
                    , ROW_NUMBER() OVER
                    (
                           ORDER BY CASE
                                  WHEN promos.Price IS NOT NULL THEN
                                        (Products.Price - promos.Price)
                                  ELSE
                                        Products.Price
                                  END
                           ASC
                    ) AS PriceRank
             FROM (SELECT ProductsCategories.ProductId, ProductsCategories.CategoryId) bpc
                    CROSS APPLY
                    (
                           SELECT TOP (1) categories.CategoryId
                                  , catpromo.Price
                           FROM
                                  (
                                        SELECT CategoryId = CAST(SUBSTRING(Hierarchy.SortPath,Tally.N,4) AS INT)
                                               , Tally.N
                                        FROM Hierarchy
                                               INNER JOIN Tally
                                                      ON Tally.N BETWEEN 1
                                                      AND DATALENGTH(Hierarchy.SortPath)
                                        WHERE Hierarchy.Id = bpc.CategoryId
                                        GROUP BY SUBSTRING(Hierarchy.SortPath,tally.N,4)
                                               , tally.n
                                  ) AS categories
                                  INNER JOIN CategoryPromotions catpromo
                                        ON categories.CategoryId = catpromo.CategoryId
                           ORDER BY categories.N DESC
                    ) AS promos
             WHERE bpc.ProductId = 1
             ORDER BY PriceRank
       ) AS XD
WHERE products.Id = 1;

这是查询结果：

为什么 ROW_NUMBER 不起作用？我可以做些什么来提高查询性能吗？这将应用于每个产品的百万行结果查询。我试图伪造 +/- 将在其中使用的结构。

期望的结果是具有最低折扣价格的第 1 行。（不能使用 MIN，因为我需要所有列）

编辑：没有 TOP (1)

Answer 1

ROW_NUMBER 工作正常。问题是您正在为 ProductCategories table 中的每一行计算它。这是您的查询的简化版本。

WITH cteProductsCategoriesDiscounts AS(
    SELECT 
          ProductsCategories.ProductId
        , ProductsCategories.CategoryId
        , promos.CategoryId AS promoCategoryId
        , Products.Price AS BasePrice
        , promos.Price
        , ISNULL(Products.Price - promos.Price, Products.Price) AS DiscountedPrice
        , ROW_NUMBER() OVER ( PARTITION BY ProductsCategories.ProductId ORDER BY ISNULL(Products.Price - promos.Price, Products.Price) ) AS PriceRank
    FROM Products
    RIGHT JOIN ProductsCategories ON Products.Id = ProductsCategories.ProductId
    CROSS APPLY (
                SELECT  TOP (1)
                          CAST(SUBSTRING(Hierarchy.SortPath,N*4-3,4) AS INT) AS CategoryId
                        , catpromo.Price
                FROM Hierarchy
                INNER JOIN Tally t ON t.N BETWEEN t.n AND DATALENGTH(Hierarchy.SortPath)/4
                INNER JOIN CategoryPromotions catpromo ON CAST(SUBSTRING(Hierarchy.SortPath,N*4-3,4) AS INT) = catpromo.CategoryId
                WHERE Hierarchy.Id = ProductsCategories.CategoryId
                ORDER BY t.N
        ) AS promos
    WHERE ProductsCategories.ProductId = 1
)
SELECT *
FROM cteProductsCategoriesDiscounts
WHERE PriceRank = 1;

编辑：进行了调整以允许使用多个产品。

ROW_NUMBER 为所有行返回相同的值（+ 查询性能）

ROW_NUMBER returning the same value for all rows (+ query performance)

tsql

sql-server

row-number