如何显示特定的字段集

Question

Select
  tblActivity.RoomID, 
  tblRoomEquipment.EquipmentType, 
  COUNT(tblActivity.Name) AS NumberOfActivities 
from tblActivity
inner join tblRoomEquipment
on tblRoomEquipment.RoomID= tblActivity.RoomID
where tblRoomEquipment.EquipmentType = 'W' 
group by tblActivity.RoomID 

在这里，我想显示具有特定设备类型的RoomID在这种情况下是'W'的次数，所以我使用了来自tbl Activity的Name列来确定W出现的次数名称ID将显示其相当混乱的解释。

因此本身就是问题所在：列出在其中包含白板的房间中发生的活动的数量。 （5）

错误：

  

Msg 8120，Level 16，State 1，Line 1 Column   'tblRoomEquipment.EquipmentType'在选择列表中无效，因为   它不包含在聚合函数或GROUP BY中   子句。

Answer 1

SELECT 
    a.RoomID, 
    re.EquipmentType, 
    COUNT(a.Name) AS NumberOfActivities 
FROM tblActivity as a
INNER JOIN tblRoomEquipment as re ON re.RoomID= a.RoomID
WHERE re.EquipmentType = 'W' 
GROUP BY a.RoomID, re.EquipmentType