Database design for an E-commerce website
If you know most of the attributes your products will have ahead of time, you could hard-code them into the tables for different product types, such as:



books
-----
  id
  price
  title
  author
  isbn
  etc....

mobile_device
-------------
  id
  price
  size
  colour
  model
  etc...



You could also try something like this:



base_product
------------
  id
  base_price
  product_type

book_product_attributes
-----------------------
  base_product_id (FK to base_product)
  title
  author

mobile_dev_product_attributes
-----------------------------
  base_product_id (FK to base_product)
  model
  colour


This way, you can group your common attributes in a base product table, and more specific attributes are stored in other tables when necessary.

This will work if your product types are mostly static. On the other hand, if you have no idea what product types or attributes you'll need in the future, and entity-attribute-value based system might work better. The idea behind that model is that you have a table for the different attributes you might have, a table for the different entities in your system, and a table for the attribute values that an entity has. Example:


entities
--------
  id

attributes
----------
  id
  name

values
------
  id
  entity_id
  attribute_id
  value


The data might look like this:



entities
ID
----
  1

attributes
ID |  name   
----------
1  |  title
2  |  author


values
ID  | attribute_id   | entity_id   | value
---------------------------------------------------------
1   | 1              | 1           | "Great Expectations"
2   | 2              | 1           | "Charles Dickens"



This data very briefly describes a product which has two attributes: title, and author, with the valus "Great Expectations" and "Charles Dickens", respectively.

Be aware that using an EAV database can make queries very awkward. With enough data and the wrong model design, it's also possible to run into performance problems. The example I gave was very simple but more realistic designs tend to be more complicated than that. It can take time to get this kind of database correct and it's not always the best solution.