Question

现在，下面的查询检索了多条产品记录。如何将结果集限制为仅检索每个product_ID的一条记录？将从不同的产品返回多个记录，但每个product_id只需要一个产品系列。这是MS SQL 2005

 SELECT DISTINCT dbo.Products.Product_ID AS Expr1,
                CASE
                                WHEN dbo.Products.thumbnail      IS NULL
                                OR              dbo.Products.thumbnail = ''
                                THEN dbo.Products.Smimage
                                ELSE dbo.Products.thumbnail
                END AS image                                                                                                            ,
                dbo.Products.ProductTitle                                                                                               ,
                '<img WIDTH="62" src="http://media.companyinc.com/companyinc/SKUimages/small/' + dbo.Products.Smimage + '">' AS URLImage,
                dbo.INV_dropshippers_To_ProductOptions.sku                                                                              ,
                dbo.Products.Discontinued                                                                                               ,
                dbo.Products.CloseOut                                                                                                   ,
                dbo.Products.Special                                                                                                    ,
                dbo.Products.Active                                                                                                     ,
                dbo.Products.location_id                                                                                                ,
                dbo.INV_dropshippers_To_ProductOptions.dropshipper_id                                                                   ,
                dbo.Products.season                                                                                                     ,
                dbo.Products.thumbnail                                                                                                  ,
                dbo.Products.Smimage                                                                                                    ,
                dbo.Products.CustomField2                                                                                               ,
                dbo.Products.pt_type                                                                                                    ,
                dbo.Products.PartNumber                                                                                                 ,
                dbo.Products.RetailPrice AS Price                                                                                       ,
                dbo.skupurchasedreport.Product_Id                                                                                       ,
                dbo.skupurchasedreport.totalprice_date1                                                                                 ,
                dbo.skupurchasedreport.totalprice_date2                                                                                 ,
                dbo.skupurchasedreport.qtypurchased_date1                                                                               ,
                dbo.skupurchasedreport.qtypurchased_date2                                                                               ,
                dbo.skupurchasedreport.totalprice_date3                                                                                 ,
                dbo.skupurchasedreport.qtypurchased_date3                                                                               ,
                dbo.INV_dropshippers_To_ProductOptions.quantity AS currentqty
FROM            dbo.Products
                INNER JOIN dbo.skupurchasedreport
                ON              dbo.Products.Product_ID = dbo.skupurchasedreport.Product_Id
                LEFT OUTER JOIN dbo.Options AS Options_2
                RIGHT OUTER JOIN dbo.INV_dropshippers_To_ProductOptions
                ON              Options_2.Opt_ID = dbo.INV_dropshippers_To_ProductOptions.option_id3
                LEFT OUTER JOIN dbo.Options AS Options_1
                ON              dbo.INV_dropshippers_To_ProductOptions.option_id2 = Options_1.Opt_ID
                LEFT OUTER JOIN dbo.Options
                ON              dbo.INV_dropshippers_To_ProductOptions.option_id1 = dbo.Options.Opt_ID
                ON              dbo.Products.Product_ID                           = dbo.INV_dropshippers_To_ProductOptions.product_id
GROUP BY        dbo.skupurchasedreport.Product_Id                    ,
                dbo.INV_dropshippers_To_ProductOptions.product_id    ,
                dbo.Products.Product_ID                              ,
                dbo.Products.ProductTitle                            ,
                dbo.Products.thumbnail                               ,
                dbo.Products.Smimage                                 ,
                dbo.INV_dropshippers_To_ProductOptions.sku           ,
                dbo.Products.Discontinued                            ,
                dbo.Products.CloseOut                                ,
                dbo.Products.Special                                 ,
                dbo.Products.Active                                  ,
                dbo.Products.location_id                             ,
                dbo.INV_dropshippers_To_ProductOptions.dropshipper_id,
                dbo.Products.season                                  ,
                dbo.Products.CustomField2                            ,
                dbo.Products.pt_type                                 ,
                dbo.Products.PartNumber                              ,
                dbo.Products.RetailPrice                             ,
                dbo.skupurchasedreport.Product_Id                    ,
                dbo.skupurchasedreport.totalprice_date1              ,
                dbo.skupurchasedreport.totalprice_date2              ,
                dbo.skupurchasedreport.totalprice_date1              ,
                dbo.skupurchasedreport.totalprice_date3              ,
                dbo.skupurchasedreport.qtypurchased_date1            ,
                dbo.skupurchasedreport.qtypurchased_date2            ,
                dbo.skupurchasedreport.qtypurchased_date3            ,
                dbo.INV_dropshippers_To_ProductOptions.quantity

Answer 1

哇，你真的想要被那么多领域分组吗？通常，当我看到表中几乎每列都有某种聚合和分组的SQL语句时，这表明它可能是错误的。它可能会返回今天的正确数据，但明天则是另一回事。阅读DISTINCT，Group By和Inner Queries以适当地处理这个问题。发布此问题的正确方法是从表中提供一些数据，并根据预期的输出或预期结果提供您想要的内容。我的倾向告诉我你想要某种

SELECT .. FROM .. INNER JOIN (SELECT ...)...GROUP BY SomeField

Answer 2

如果您希望每个产品ID获得一个结果，那么您必须在除产品ID之外的所有其他列上获取MAX，然后仅按产品ID进行分组。这可能会导致其他问题，因此您需要了解其后果，更重要的是，您需要了解数据的性质。

Answer 3

我会尝试解释这项技巧，但会由您来解决问题。

让我们从表开始：

DECLARE @tbl TABLE ( Id int, Color varchar(10) )

INSERT INTO  @tbl
        ( Id, Color )
SELECT  1 ,'BLUE' UNION
SELECT  2 ,'BLUE' UNION
SELECT  3 ,'RED' UNION
SELECT  4 ,'GREEN' UNION
SELECT  5 ,'GREEN' UNION
SELECT  6 ,'GREEN' UNION
SELECT  7 ,'YELLOW' UNION
SELECT  8 ,'YELLOW';

现在我想只列出每种颜色的一个项目（类似于你的问题）

WITH  abcd
        AS ( SELECT Id
                   ,Color
                   ,ROW_NUMBER() OVER ( PARTITION BY Color ORDER BY Id ) AS rn
             FROM   @tbl
           )
  SELECT  Id ,Color
  FROM    abcd
  WHERE   rn = 1

返回

Id          Color
----------- ----------
1           BLUE
4           GREEN
3           RED
7           YELLOW

根据product_id返回不同的产品

3 个答案: