How to start the DataBase design for a web project?

I plan to develop a web directory system.(php used)

But i don't kno开发者_开发问答w how to start the Data Base design.

Are there any good books/tutorials about it? Thank you.

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Questions you should ask yourself (or the product owner) are:

• What entities are at the heart of your application?
• How are they linked to each other?

My guess: Web directory system has got:

• Entries
• Categories
• Tags
• Users

Now take it further.. how are these related to each other?

• Entries belong to categories
• Tags are associated with entries
• Entries are submitted by users

And another step..

• Entries have titles, descriptions, images, links, contact info
• Users have usernames, emails, passwords

.. and so on