Question

我坚持建立一个复杂的查询，并希望有人可以帮助我，如果它可能的话。我有一个表“竞争对手”，这里有一些列：

Type | Brand | Model | Date | Resolution | etc.

该表格将有重复的Model条目（明显相同Brand，但可能有不同的Type（两种可能的类型：'ProAV'和'Disti'））。我需要构建一个输出如下表的查询：

Top (ProAV) | Top (Disti) | Last Occurrence | Brand | Model | Resolution | etc.

基本上我需要一个能够获得不同类型，品牌和型号的查询，但要计算找到多少重复项并将该数字放入Top（ProAV）或Top（ Disti），以Type为准。我需要从重复项中提取最近的（给定日期），以便我可以将其日期作为Last Occurrence字段。我希望这是有道理的，如果没有，请告诉我。非常感谢！

Answer 1

SELECT SUM(CASE WHEN Type = 'ProAV' THEN 1 ELSE 0 END) AS TopProAV,
       SUM(CASE WHEN Type = 'Disti' THEN 1 ELSE 0 END) AS TopDisti,
       MAX(Date) AS LastOccurence,
       Brand, Model, Resolution
    FROM Competitor
    GROUP BY Brand, Model, Resolution

编辑：根据评论，您可以使用子查询或CTE来完成您想要的操作。类似的东西：

WITH cteMaxDate AS (
    SELECT SUM(CASE WHEN Type = 'ProAV' THEN 1 ELSE 0 END) AS TopProAV,
           SUM(CASE WHEN Type = 'Disti' THEN 1 ELSE 0 END) AS TopDisti,
           MAX(Date) AS LastOccurence,
           Brand, Model, Resolution
        FROM Competitor
        GROUP BY Brand, Model, Resolution
)
SELECT md.TopProAV, md.TopDisti,
       md.LastOccurentce, 
       md.Brand, md.Model, md.Resolution,
       c.AdditionalColumn1, c.AdditionalColumn2
    FROM cteMaxDate md
        INNER JOIN Competitor c
            ON md.Brand = c.Brand
                AND md.Model = c.Model
                AND md.Resolution = c.Resolution
                AND md.LastOccurence = c.Date

Answer 2

您的Type数量有限吗？在这种情况下，您可以使用pivot解决您的问题更具体地说，对于表

Type    Model
----    -----
A       X
B       X
C       Y
A       Z
NULL    NULL

您运行此查询

Select Model, [A], [B], [C]
From
(select Model, Type
from dbo.Competitor) as SourceTable
PIVOT
(Count([Type]) for [Type] in ([A], [B], [C])) as PivotTable

获取

Model    A    B    C
------   -    -   -
X        1    1   0
Y        0    0   1
Z        1    0   0

帮助sql查询

2 个答案: