SQL GROUP BY用于计算行的数量，而不是数量的总和

如果一个国家的一个小部件的类别中有多个小部件，我尝试通过分组获得计数1

为了更好地解释这一点，以下是我目前获得的代码：

select c.Name As Country, w.Description As WidgetName, cat.Description As Category,
  COUNT (wc.Id)AS Clicks  
  from ManufacturerWidgets mw
 join WidgetClicks wc on mw.Id = wc.ManufacturerWidgetId
 join Products p on   wc.ProductId = p.Id
 join Countries c on mw.CountryId = c.Id
 join Widgets w on w.Id = mw.WidgetId
 join Categories cat on cat.Id = p.CategoryId
 where mw.Enabled = 1 and  mw.ManufacturerId = 17 and wc.CreatedAt >= '2013-01-01 00:00:00.000' and wc.CreatedAt <= '2013-07-05 23:59:00.000'
 GRoup By wc.WidgetImpressionId, c.Name,  w.Description,  cat.Description
 HAVING wc.WidgetImpressionId > 0
 order by  c.Name, w.Description, cat.Description

我需要返回的是每个类别的inteeraction，因此：

Austria  onebysix     computing   4  - this would be 1 not 4

我需要按类别对它们进行分组，这样最终结果将是：

Austria  onebysix     computing   2
Austria  onebysix     printing    3

---

将wc.WidgetImpressionID从分组中删除。这是添加额外的分组级别，该级别恰好是所需结果的计数

将

计数更改为
计数（wc.widgetmepressionid）
分别给出2和3

HAVING应该是
HAVING COUNT（wc.widgetmepressionid）>0
。在您的代码中，它的作用类似于WHERE子句过滤器，因为它位于GROUPBY中（请参阅上面的第一点）

选择c.名称作为国家，w.描述作为WidgetName，类别描述作为类别，
将（wc.widgetmepressionid）计数为单击次数
来自制造商Widgets mw
在mw.Id=wc.ManufacturerWidgetId上加入WidgetClicks wc
在wc.ProductId=p.Id上连接产品p
在mw.CountryId=c.Id上加入国家c
在w.Id=mw.WidgetId上加入小部件w
在cat.Id=p.CategoryId上连接类别cat
其中mw.Enabled=1，mw.ManufacturerId=17，wc.CreatedAt>='2013-01-01 00:00:00.000'和wc.CreatedAt 0
按c.名称、w.说明、类别说明订购
Hi-gbn这似乎是在把点击数加在一起-所以对于计算，我得到了5次，对于打印，我得到了6次，而不是2次和3次，我是否遗漏了什么？没有样本数据，我们只能猜测。请尝试计数（DISTINCT wc.widgetmepressionid）

Austria  onebysix     computing   2
Austria  onebysix     printing    3

select c.Name As Country, w.Description As WidgetName, cat.Description As Category,
  COUNT (wc.WidgetImpressionID) AS Clicks  
  from ManufacturerWidgets mw
 join WidgetClicks wc on mw.Id = wc.ManufacturerWidgetId
 join Products p on   wc.ProductId = p.Id
 join Countries c on mw.CountryId = c.Id
 join Widgets w on w.Id = mw.WidgetId
 join Categories cat on cat.Id = p.CategoryId
 where mw.Enabled = 1 and  mw.ManufacturerId = 17 and wc.CreatedAt >= '2013-01-01 00:00:00.000' and wc.CreatedAt <= '2013-07-05 23:59:00.000'
 GRoup By c.Name,  w.Description,  cat.Description
 HAVING COUNT(wc.WidgetImpressionID) > 0
 order by  c.Name, w.Description, cat.Description