Sql server 如何显示特定的字段集

在这里，我想显示具有特定设备类型的RoomID的次数在本例中为“W”，因此我使用tbl活动中的“名称”列来确定，这意味着该ID在该名称中出现的次数将被显示，这很难解释

问题就在这里：列出在有白板的房间里进行的活动的数量。(五)

错误：

Msg 8120，16级，状态1，第1行列 “tblRoomEquipment.EquipmentType”在选择列表中无效，因为 它既不包含在聚合函数中，也不包含在GROUP BY中 条款

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将EquipmentType添加到group by？只缺少一件事，非常感谢：）

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 

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