I have simple database.
It contains 2 tables.
Rooms
Reservations
They is relations via room ID.
How can I prevent in Reservation table to do not make a reservation for one room in the same date?
you can insert an unique constraint on fields (roomID and reservationDate).
In this way you'll can have only a reservation for a room in a date.
If you want to unlock a room, you'll have to delete a reservation row.
Related
I have a database of 5 tables. Some contain the same columns as others, does tying these tables to another table which has the primary keys of other tables meet 3rd normalisation. (This is outlined more clearly below)
I have a table of customers, with their names and phone numbers as well as requirements they want in their car etc. The primary key is CustomerID.
I then match a customer with a car which matches their requirements. I have a table with Match ID (Primary key) and CustomerID and CarID (As foreign keys.)
By doing this, can I then make a table off Match ID which can be given to the receptionist so that they can contact the customer. In this table I would need to include the customer name and phone number. However, does this break 3rd normal form as Phone number is now both in CustomerID and the new table.
The last table you describe doesn't necessarily break any normal form, because the customer's phone number can change in the future. You may want to preserve the phone number in another table so there is a record of what phone number was contacted on that date.
Compare with a database of products. The product table has prices. Then you record customer purchases, with a copy of the price they paid on the date they made the purchase. That's okay because you need a record of what was paid in each case. A customer may buy the product during a sale, or they got a senior discount, or a bulk discount, or the price may change a month after they bought the item, etc. The price they paid is not necessarily the current price recorded in the products table. Therefore it does not violate 3NF.
I'm trying to implement a flight booking system, and the use case is as follow:
A registered customer should be able to buy several tickets, not only for himself, and for each ticket the passenger info would be recorded.
In the database design, I have two tables -- a ticket table, and a purchase table. Tuples in the ticket table records only information with the flight and the passenger, and each ticket has a unique ticketID as primary key. Inside the purchase table, it has a foreign key reference to the ticket table, and has attributes that indicate which registered use this purchase record belongs to.
Now, suppose I have several tuples of passenger data sent to the server, the first thing I should do is to insert new tickets, and then I could perform insertion on the purchase table indicates the relation between each tickets and the person who bought the tickets. Notice that the new records in the purchase table would have ticket_ids which were just created by new tickets.
My confusion is: how do I implement this within one operation as a whole? ** In the purchase table, I would also give the tuples that are created by the same customer in the same transaction an ID, indicates that those tickets belongs to the same purchase records. ** Could I achieve this using a stored procedure? I feel like the passing of data is tricky, since I'm very new to stored procedure, etc.
I have records table with booking records info (8 columns). And I want to add to a record information about extra services that a client booked. I created extra_services table, but how can I specify multiple extra services to one record in records table?
If I add 9th column with just one id of extra service then there will be redundancy problem.
It depends a little on what is the content of the extra_services table. If it does contain a set of extra services that can be booked you need a table to cross reference the bookings with the extra_services.
If on the other hand you are storing the booked extra services belonging to the record you can just use a ForeignKey field to the index of the records table in the extra_services table, that way you can track which records in extra_services belong the booking record.
I'm running for office and have created a web app for tracking my door knocks to voters at their homes. The database contains a table called voters that contains all the necessary information about voters in my community.
I'd like to add a new feature to track donors to my campaign. Not all of these donors live in the community and do not vote in the district where I'm running for office. I do not need to track the same kind of info for these individuals as I do for the voters so I'm going to place these individuals into a table called nonvoters.
Now, the individuals in my "voters" table can also make donations, and I want to track those as well.
To track the donations from both voters and nonvoters, I'd like to set up a new table called "donations." This table would contain the appropriate details about the donation.
But I'm uncertain as to what the best structure is for linking the donations table to the "voters" and "nonvoters" table. If I create a column called voter_id in the table to key it to the donors information, there's no way to know which table that ID refers to. So do I set up two columns, nonvoter_id and voter_id and insert the ID into the applicable column depending on whether the donor is a voter? This seems weird.
Or maybe I create a column in both the voters and nonvoters table called donor_id that I can use to link my data in the donations table. If I went this route, it seems like I'd have to do a some behind the scenes work to ensure the donor_id was unique and was keyed to the data inside the donations table.
Or maybe there are other approaches I'm not familiar with. Any guidance is appreciated.
I would use a single table for voters and non-voters, let's say persons. You can have a flag in the persons table that indicates if the person is a voter or you may even derive this from their address (if that's possible).
I would create a donations table and link each donation to a person (or persons) in the persons table using the id in the persons table. If a donation can be given by multiple people, then you will need a 3rd connection table with person id and donation id as 2 fields. These 2 fields would be the primary key for the connection table.
I have a table for guests, each guest with a unique name.
I have a table for guest_transactions with guest_id, status_id, arrived_time, left_time.
And a status table with a name column, populated with values (here, leaving, left).
I want to record guests as they come and go, but I'd like to have a constraint which prevents a guest from arriving twice before leaving. Is there a way to do this?