Question

所以我需要加入三个表，然后选择一个月的平均星数，我们会说6月，然后每个类别选择所有的业务。到目前为止，我有：

SELECT  B1.Name, B2.Category, AVG(R1.Stars) as Average
FROM Business B1
INNER JOIN Reviews R1
ON B1.ID=R1.BusinessID 
INNER JOIN BusinessCategories B2
ON B2.BusinessID=R1.BusinessID
WHERE R1.Date >= convert(datetime,'01-6-2011') AND R1.Date <= convert(datetime,'30-6-   2011')
GROUP BY Name, Category
ORDER BY Category, AVG(R1.Stars) DESC

这让我了解每个企业的平均值，但我不知道如何为每个类别选择顶部。

更新：添加我目前所拥有的样本输出以及我正在寻找的内容：

这是我现在得到的：

Victoria Secrets    Accessories 5
Francesca's Collections Accessories 5
Saint 22    Accessories 4
Loehmann's Inc  Accessories 3
Arcadia Ice Arena   Active Life 5
Arizona Sunrays Gymnastics & Dance Center   Active Life 5
Blissful Yoga Studio    Active Life 5
Corner Archery  Active Life 5
Imagination Avenue  Active Life 5
Jump Street Active Life 5
Life Time Fitness   Active Life 5

但我想要的是：

Victoria Secrets    Accessories 5
Arcadia Ice Arena   Active Life 5
Video Paradise  Adult   5

或者我想更好的是，如果有一个平局，就像一堆活跃的生活类别，我们会回到该类别的所有顶级企业。

Answer 1

试试这个：

SELECT T1.Name, T1.Category, T1.Average
FROM
(SELECT  B1.Name, B2.Category, AVG(R1.Stars) as Average
FROM Business B1
INNER JOIN Reviews R1
ON B1.ID=R1.BusinessID 
INNER JOIN BusinessCategories B2
ON B2.BusinessID=R1.BusinessID
WHERE R1.Date >= convert(datetime,'01-6-2011') AND R1.Date <= convert(datetime,'30-6-   2011')
GROUP BY Name, Category
ORDER BY Category, AVG(R1.Stars) DESC) T1

LEFT JOIN (
SELECT  B1.Name, B2.Category, AVG(R1.Stars) as Average
FROM Business B1
INNER JOIN Reviews R1
ON B1.ID=R1.BusinessID 
INNER JOIN BusinessCategories B2
ON B2.BusinessID=R1.BusinessID
WHERE R1.Date >= convert(datetime,'01-6-2011') AND R1.Date <= convert(datetime,'30-6-   2011')
GROUP BY Name, Category
ORDER BY Category, AVG(R1.Stars) DESC) T2 on T2.Average> T1.Average AND T1.Category= T2.Category
WHERE T2.Name IS NULL

或

SELECT Name,Category,Average FROM ( SELECT ROW_NUMBER() OVER(Partition By Category ORDER BY AVG(R1.Stars) DESC) as RN, B1.Name, B2.Category, AVG(R1.Stars) as Average FROM Business B1 INNER JOIN Reviews R1 ON B1.ID=R1.BusinessID INNER JOIN BusinessCategories B2 ON B2.BusinessID=R1.BusinessID WHERE R1.Date >= convert(datetime,'01-6-2011') AND R1.Date <= convert(datetime,'30-6- 2011') GROUP BY Name, Category ORDER BY Category, AVG(R1.Stars) DESC ) T WHERE RN=1

Answer 2

使用max（R1.Stars）代替avg（R1.Stars）

Answer 3

试试这个：

SELECT FIRST(Name) AS BName, Category, MAX(Average) AS TopAverage
FROM (
    SELECT  B1.Name, B2.Category, AVG(R1.Stars) as Average
    FROM Business B1
    INNER JOIN Reviews R1
    ON B1.ID=R1.BusinessID 
    INNER JOIN BusinessCategories B2
    ON B2.BusinessID=R1.BusinessID
    WHERE R1.Date >= convert(datetime,'01-6-2011') AND R1.Date <= convert(datetime,'30-6-   2011')
    GROUP BY Name, Category
) q
GROUP BY Category
ORDER BY Category, TopAverage DESC

加入3个表格，只选择每个类别的最高平均值

3 个答案: