Question

I’m beginning to build a stamp collecting web app. Python/flask backend (i think :)) mySQL as db. I don’t know much about db design so please keep that in mind if I do some really stupid mistake in the way I thought it out. I was thinking of splitting the data into 3 tables.

• users table (all the users should be added upon registration to this table)
• stamps table (all stamps should reside here and only modified by me)
• owned table (junction table with user_id and stamp_id as foreign keys)

Question : if I put user_id and stamp_id as primary key , there will only be one unique entry of this type for example user_1 has card_1. But user_1 might have a duplicate of card_1 so i should have 2 rows
user_1 card_1
user_1 card_1
Another problem that arises is that I want to include state of owned stamp. For example user_1 might have a card_1 in mint condition and a card_1 in bad condition. As far as I understand I can only enter one unique pair of user_1 card_1 . What can I do to get the desired result? Also if there’s a better way of doing this please let me know.

Aditional question. I was using mysql workbench to try to plot the db so I have a question about the sql it generates. the CONSTRAINT “fk_gibberish”, is that normal or … why is that ?

CREATE  TABLE IF NOT EXISTS `stampcollect`.`users` (
  `user_id` INT UNSIGNED NOT NULL AUTO_INCREMENT ,
  `user_username` VARCHAR(45) NULL ,
  `user_password` VARCHAR(45) NULL ,
  `user_email` VARCHAR(45) NULL ,
  PRIMARY KEY (`user_id`) )

CREATE  TABLE IF NOT EXISTS `stampcollect`.`stamps` (
  `stamp_id` INT UNSIGNED NOT NULL AUTO_INCREMENT ,
  `stamp_name` VARCHAR(45) NULL ,
  PRIMARY KEY (`stamp_id`) )

CREATE  TABLE IF NOT EXISTS `stampcollect`.`owned` (
  `user_id` INT NOT NULL ,
  `stamp_id` INT NOT NULL ,
  `stamp_status` BIT NULL ,
  PRIMARY KEY (`user_id`, `stamp_id`) ,
  INDEX `fk_{F5DBEF0D-24E0-4AFF-A5CB-2A6A0D448C96}` (`stamp_id` ASC) ,
  CONSTRAINT `fk_{22B4468E-A5FB-4702-A8A9-576AA48A0543}`
    FOREIGN KEY (`user_id` )
    REFERENCES `stampcollect`.`users` (`user_id` ),
  CONSTRAINT `fk_{F5DBEF0D-24E0-4AFF-A5CB-2A6A0D448C96}`
    FOREIGN KEY (`stamp_id` )
    REFERENCES `stampcollect`.`stamps` (`stamp_id` ));

Answer 1

If users can own the same stamp in multiple states then the state should go in the “owned” table and be part of the key. If he can own multiple copies of the same stamp then it would make sense to have a “quantity” column in that table (not part of the key).