Shopping Cart tables - Feedback Database Design

I am developing online shopping system.

This is how the product structure work:

There are number of categories..

Each Category has number of items.

Each Item have one or more Options

An Option can have extra(s) or without extra(s)

The following tables I have:

mysql> desc categories;
+------------+--------------+------+-----+---------+----------------+
| Field      | Type         | Null | Key | Default | Extra          |
+------------+--------------+------+开发者_JAVA百科-----+---------+----------------+
| cat_id     | int(11)      | NO   | PRI | NULL    | auto_increment |
| company_id | int(11)      | NO   |     | NULL    |                |
| name       | varchar(100) | NO   |     | NULL    |                |
+------------+--------------+------+-----+---------+----------------+

Eg: 12, 2, "Google"

Items Table:

mysql> desc items;
+-------------+--------------+------+-----+---------+----------------+
| Field       | Type         | Null | Key | Default | Extra          |
+-------------+--------------+------+-----+---------+----------------+
| item_id     | int(11)      | NO   | PRI | NULL    | auto_increment |
| cat_id      | int(11)      | NO   |     | NULL    |                |
| name        | varchar(150) | NO   |     | NULL    |                |
| description | varchar(150) | NO   |     | NULL    |                |
+-------------+--------------+------+-----+---------+----------------+

Eg: 2, 12, "Item 1", "Desc... 1"

Eg: 3, 12, "Item 2", "Desc... 2"

Options Table

mysql> desc items_options;
+-----------+--------------+------+-----+---------+----------------+
| Field     | Type         | Null | Key | Default | Extra          |
+-----------+--------------+------+-----+---------+----------------+
| option_id | int(11)      | NO   | PRI | NULL    | auto_increment |
| item_id   | int(11)      | NO   |     | NULL    |                |
| name      | varchar(150) | NO   |     | NULL    |                |
| price     | decimal(6,2) | NO   |     | NULL    |                |
+-----------+--------------+------+-----+---------+----------------+

Eg: 45, 2, "Regular", "2.20"

Eg: 46, 3, "Small", "1.20"

Eg: 47, 3, "Large", "2.20"

Extras Table:

mysql> desc items_options_extras;
+-----------+--------------+------+-----+---------+----------------+
| Field     | Type         | Null | Key | Default | Extra          |
+-----------+--------------+------+-----+---------+----------------+
| extra_id  | int(11)      | NO   | PRI | NULL    | auto_increment |
| option_id | int(11)      | NO   |     | NULL    |                |
| name      | varchar(150) | NO   |     | NULL    |                |
| price     | decimal(6,2) | NO   |     | NULL    |                |
+-----------+--------------+------+-----+---------+----------------+

Eg: 64, 47, "With Bag", 0.10"

Is this good database design? What could be improved?

I did not create a relationship table, is this necessary? If so, im not sure how do I create a relationship table.

At the moment I use multiple SELECT queries to get the relationship between those tables, like this below:

<?php
$q =  mysql_query("SELECT item_id, name FROM items where cat_id = '3'");
while($row = mysql_fetch_assoc($q)) {
     echo $row['name'];
     $q2 = mysql_query("SELECT price FROM items_options_extras where item_id =" . $row['item_id']);
        while($row2 = mysql_fetch_assoc($q2))
            echo $row2['price'];
        }
}
?>

When I want to delete an Item and including options, I use similar php code like above.

Edit: Forgot to add Options table

Edit: Updated some data example.

Consider that an Item may belong to multiple Categories.

Here are things to consider:

• If the price of an item changes with the category, then the ItemPrice column goes into the CategoryItems table. If not, it goes into the Items table.
• If the price of an option changes with the item, then the OptionPrice column goes into the ItemOptions table. If not, it goes into the Option table.