Correct database? Does it need altering? - mysql

Question

I'm creating a page where I want users to be able to book a seat for an event.
1 user can only book 1 seat
users have no seat selected upon login, first after buying into a spot
Need to able to clear seats table, without loosing anything from user-table (except of course the assigned seats.)
I've created two tables, and since I'm pretty new to mySQL, I wanted to check if this was done correctly:
members-table:
user_id int(8) Not null auto_increment
user_name varchar(30) Not null
user_pass varchar(255) Not null
seat_ID smallint(6) Yes NULL
seats-table
seat_ID smallint(6) No auto_increment
user_id smallint(6) Yes NULL
seat_status tinyint(4) Yes NULL
seat_status tinyint(4) Yes NULL
I've created 2 FK-refs:
ALTER TABLE seats
ADD CONSTRAINT FK_seats
FOREIGN KEY (user_id) REFERENCES members(user_id)
ON UPDATE CASCADE
ON DELETE CASCADE;
ALTER TABLE seats
ADD CONSTRAINT FK_seats
FOREIGN KEY (seat_ID) REFERENCES members(seat_ID)
ON UPDATE CASCADE
ON DELETE CASCADE;
Am I on the right track? Will I be able to progress to a decent final product with this setup? suggestions/improvements? I don't want to start all over in a couple of weeks because the database structure is of poor quality.

Answer 1

First of all I don't see why you're using a second table if any user can only hold one seat at any given time, secondly user_id in seats-table should be the same size as user_id in members table namely int(8), otherwise you won't be able to seat users after a while, third issue is the duplication of seat_status, I suppose that was a mistake or you had another name for it.
In my opinion a better idea is to use a single table if it's a 1->1 mapping and define it as
CREATE TABLE `members-table` (
user_id int(8) not null auto_increment,
user_name varchar(30) not null,
user_pass varchar(255) not null,
seat -- your type choice, should be nullable if not seated
);
Clearing the seats with this config would be as simple as
UPDATE `members-table` SET `seat` = NULL;

Answer 2

CREATE TABLE `seats` (
id int(4) unsigned not null auto_increment primary key,
row int(2) unsigned not null,
col int(2) unsigned not null,
UNIQUE(row, col)
) ENGINE InnoDB;
CREATE TABLE `members` (
user_id int(8) not null auto_increment primary key,
user_name varchar(30) not null,
user_pass varchar(255) not null,
seat int(4) unsigned null,
FOREIGN KEY(seat) references seats(id) on delete set null on update restrict,
UNIQUE(seat)
) ENGINE InnoDB;
You will have to populate the seats database with all available rows and columns, use null on id when inserting to use the auto_increment feature!
Check if a seat is taken
SELECT COUNT(*) AS occupied FROM members WHERE seat = (SELECT id FROM seats WHERE row = :ROW AND col = :COL);
Alternatively use SELECT (1 - COUNT(*)) AS vacant in the query above if it's more conveninent for you.
Find first free seat
SELECT MIN(id) FROM seats WHERE NOT EXISTS( SELECT seat FROM members WHERE seat = seats.id);
Unassign all taken seats
UPDATE members SET seat = NULL;