Question

I’m having trouble with my sqlite database. I’m trying to write an query that will generate a total bill for a specific guest (guestID)

GUEST

• GuestID (Primary Key, Type:Integer, Auto increment)
• FName (Type:Text)
• LName (Type:Text)

RESERVATION

• Reservation Number (Primary Key, Type: Integer, Auto increment)
• CheckIN (Type:DateTime)
• CheckOUT (Type:DateTime)
• GuestID (Type:Integer)
• RoomNumber (Type: Integer)

ROOM

• RoomNumber (Primary Key, type: Integer)
• RoomTypeID (type: Integer)

ROOMTYPE

• RoomTypeID (Primary Key, type: Integer)
• Bed (type: Text)
• Price (type: Integer)

I know that I would have to subtract Reservation.checkout from Reservation.checkin to get the number of days then multiply that by the RoomType.price so that would give me a total bill. So how would I write my sql query to give me a total bill for a specific guest (guestid)? I know you can join up to three tables but I don’t know how to join these four tables. Please help. Thank you in advance.

Answer 1

2 ways are 1 in the sql or 1 in the application level
1) sql:

SELECT g.*, ((strftime('%s',r.CheckOUT) - strftime('%s',r.CheckIN)) * rt.Price/24/60/60) AS total
FROM GUEST g, RESERVATION r, ROOM rm, ROOMTYPE rt
WHERE g.GuestID = r.GuestID AND r.RoomNumber = rm.RoomNumber AND
rm.RoomTypeID = rt.RoomTypeID

You can modify to your needs basically the statement is to get the columns in guest table and compute the price he/she needs to pay by subtracting the check out and check in dates in seconds and multiply by the price down to per seconds.

2) app level:
You can probably run 2 sql statements to get the price of the particular room for particular guest.
Do the computation of price in your whatever language you are using php/ruby/java etc.