两个查询到一个表中有两列

Question

我有一个名为Rooms的表，看起来像这样

间

id    name   room number 
-------------------------
1     Dave   Room 100  
2     NULL   ROOM 101    
3     Scott  Room 100    

我需要检查哪个房间是空的，哪个房间有人关联，所以结果将是：

Room name  Count        
-----------------
Room 100   2      -- Because Dave and Scott is in the room
Room 101   0      -- No name is associated with the room 

我刚开始学习SQL，所以我的知识有限我能看到的是

SELECT Count(room_number) 
  FROM rooms 
 WHERE name != NULL 

...将根据room_number在列表中显示的次数返回2和0，并且与之关联的名称不是0并且

SELECT DISTINCT(room_number) 
  FROM rooms 

...将返回100室和101室

如何组合这两个查询以获得我想要的结果表？

Answer 1

SELECT RoomNumber, COUNT(Name)
FROM rooms
GROUP BY RoomNumber

我建议添加Room表并将RoomNumber更改为外键关系。标准化该列。

Answer 2

SELECT COUNT(NAME), RoomNumber
FROM ROOMS
GROUP BY RoomNumber