Question

我有这个：

SELECT Product.ProductID, Product.Name, Product.GroupID, Product.GradeID,
       AVG(tblReview.Grade) AS Grade
FROM   Product left Join tblReview ON Product.GroupID = tblReview.GroupID
WHERE  (Product.CategoryID = @CategoryID)
GROUP  BY Product.ProductID, Product.Name, Product.GroupID, Product.GradeID

我想只返回Product.Name唯一的行。如果我创建SELECT DISTINCT ProductID每行都不同，那么所有行都是唯一的。

Answer 1

你可以做这样的事情（见下文），但这假设你不在乎两个同名的产品是否有不同的GroupID等，因为你不能真正列出那些，除非你使用不同的方法（多个查询）。

SELECT        Product.Name
            , max(Product.ProductID) as ProductID
            , max(Product.GroupID) as GroupID
            , max(Product.GradeID) as GradeID,
            , AVG(tblReview.Grade) AS Grade
FROM            Product left Join tblReview ON Product.GroupID = tblReview.GroupID

WHERE        (Product.CategoryID = @CategoryID)

GROUP BY Product.Name

HAVING COUNT(distinct Product.Name) = 1

Answer 2

这对你有用吗？

SELECT Product.ProductID, Product.Name, Product.GroupID, Product.GradeID, 
       AVG(tblReview.Grade) AS Grade 
FROM   Product left Join tblReview ON Product.GroupID = tblReview.GroupID 
WHERE  (Product.CategoryID = @CategoryID) 
GROUP  BY Product.ProductID, Product.Name, Product.GroupID, Product.GradeID 
HAVING COUNT(Product.Name)=1

Answer 3

SELECT  p.ProductID, p.Name, p.GroupID, p.GradeID,
        (
        SELECT  AVG(grade)
        FROM    tblReview r
        WHERE   r.GroupID = p.GroupID
        ) AS Grade
FROM    (
        SELECT  *,
                ROW_NUMBER() OVER (PARTITION BY name ORDER BY productID) AS rna,
                ROW_NUMBER() OVER (PARTITION BY name ORDER BY productID DESC) AS rnd
        FROM    Product
        WHERE   CategoryID = @CategoryID
        ) p
WHERE   rna = rnd

在SQL Server中检索多行但仅在一个上进行不同的过滤

3 个答案: