```
My table
room_name    |   datecount | percentage
Room1A       |   7         |
Room2A       |   3         |
Room3A       |   2         |
Room5B       |   1         |

SELECT r.room_name,datediff(b.dateout,f.datein) as datecount
FROM room r INNER JOIN form f ON r.room_name=f.room_name INNER JOIN bill b 
ON f.ID=b.Form_ID 
GROUP BY r.room_name

```

I want to calculate the percentage 
so that [ Room1A | 7 | 54%]