Question

A noob question. I’m putting together my first database and have the following design problem: I have a class which defines a book (e.g. it’s title) and a class which defines a page (e.g. it’s design).

The table for the class book would look so:

Title        | PAGE1        | PAGE2        | PAGE3
Book-One     | SAMPLE1-UUID | SAMPLE2-UUID | SAMPLE3-UUID
Book-Two     | SAMPLE4-UUID | SAMPLE5-UUID | SAMPLE6-UUID

The table for the class page:

UUID         | FONT         | CONTENTS etc.
SAMPLE1-UUID | Times        | Example
SAMPLE2-UUID | Arial        | Example Two
SAMPLE3-UUID | Verdena      | Example Three

Now, as each page is unique and can’t be re-used in another book, I can’t use a many-to-many relationship for Pages. I could use Foreign-Key to link the two tables, i.e. link SAMPLE1-UUID of the Books Table with the SAMPLE1-UUID of the Pages Table. This has the advantage of not creating the same entry twice.

However, I don’t like the idea of having a fixed amount of rows for my pages. In the above example for the class Book, I’d have to define a certain set of Pages, like PAGE1, PAGE2, PAGE3, PAGE4, … PAGE99. Ideally, all I need is a flexible list of pages for my book class, like so:

Name         | Pages
Book-One     | "SAMPLE1-UUID, SAMPLE2-UUID"
Book-Two     | "SAMPLE4-UUID, SAMPLE5-UUID, SAMPLE6-UUID"

Pages would be a simple CharField and its contents would be a list. But then I have the problem that the two tables are not linked anymore and that I’d have to create each entry twice (i.e. I would have to enter SAMPLE1-UUID in both the pages and books table).

Is there another way to design this database? Thanks for any suggestion!

Answer 1

I’ll suggest you don’t have the pages as columns:

The table for the class book would look so with book only information:

Title        | ISBN         
Book-One     | XXXXXXXXXXXX 
Book-Two     | YYYYYYYYYYYY 

The table for the class page:

BOOKID       |PAGE_NUM | FONT         | CONTENTS
1            |1        | Times        | Example
1            |2        | Arial        | Example Two
2            |1        | Verdena      | Example Three

Your class design would look something like:

class Book(models.Model):
    title = models.CharField(max_length=100)
    isbn = models.CharField(max_length=100)

class Page(models.Model):
    book = models.ForeignKey(Book)
    page_num = models.IntegerField()
    font = models.charField(max_length=100)
    content = models.TextField()

You can go ahead and have contraints so that a book and page_num does not repeat for instance but this can be a good start.