mysql db structure and relationship - php

Question

I need help in how to setup my tables in my mysql database.
I have an user. An user gets 10 tokens to use as they wish. A token can be used only for one thing only. They can use it to create a cartoon page, game page, bio page, question page, and etc. The token can be reassigned to another page also.
I want to see what the best way to structure my database would be and the relationships.
I am thinking of having a user table, token table, cartoon table, game table, bio table, and question table. But how do I relate to all of them.

Answer 1

Relational database table design is not a hard science. It's a highly flexible paradigm that can and will change depending on the nature of your application. That being said, there are certain design principles which you should typically adhere to. See e.g. http://en.wikipedia.org/wiki/Database_design.
That being said, I'll take a shot at this from an approach that seems highly dynamic, since I'm not sure about the application specifics. Firstly, you will most definitely need a users table that might look like:
users:
first_name
last_name
user_id
n_tokens
I put this here in case a user's number of tokens is dynamic
Now that you have a way of specifying a user, you'll want to see how that user has used his/her tokens:
tokens:
token_id
This is used to specify what this (or these) token(s) are used for.
user_id
This should have a duplicate foreign key constraint on users.user_id.
n_tokens
This is different from users.n_tokens. It is not clear from your problem
whether or not you'll always have 1 token per feature. This value is a
forward-looking approach at possible future enhancements.
pagetype_id
This is to specify what type of page type the token is used for. It'll have
a foreign key constraint on pagetypes.pagetype_id (see below).
As noted above, you want people to use tokens on specific page types, like cartoon pages, bio pages, etc. which this table defines:
pagetypes:
pagetype_id
Used to define a unique identifier to this type of page
pagetype_name
String field to label the page types, e.g. "cartoon," "bio," etc.
Now, you may have several tables defining the types of pages, so I'll specify the layout for just one:
bio_pages:
pagetype_id
This id has a duplicate foreign key constraint on pagetypes.pagetype_id.
The value will ALWAYS be constant for this table. This is not the most
normalized design, as you MAY want to have a more generic 'pages' table,
but several complex joins can be confusing to some developers and even
worse, slow for queries.
token_id
Foreign key constraint on tokens.token_id.
OTHER
The rest of the fields are user-defined, as you wish to specify what
belongs on a bio page.
SUMMARY
To summarize the above table layouts, you'll want to design the database so that self-contained entities do not span multiple tables, and multiple entities don't combine into one table. With that said, I separated out the users table from the tokens table from the different <pagetype>_pages tables. To make the design more intuitive I'll make some sample queries that might help with your understanding of the layout.
To get all the bio pages that a user has created:
SELECT bio_pages.*
FROM bio_pages
INNER
JOIN tokens
ON bio_pages.token_id=tokens.token_id
INNER
JOIN users
ON tokens.user_id=users.user_id
WHERE users.first_name='john'
AND users.last_name='doe'
To get the total number of coins that a user has used, and also the maximum number of coins they can use:
SELECT SUM(tokens.n_tokens) AS used_tokens,
users.n_tokens AS max_tokens
FROM tokens
INNER
JOIN users
ON tokens.user_id=users.user_id
WHERE users.first_name='john'
AND users.last_name='doe'
GROUP BY users.user_id
Hopefully this all makes sense and is intuitive. Please let me know if anything is unclear.