Designing E-commerce database and mysql error - mysql

Question

I am trying to make an e-commerce site from scratch. Currently I am trying to make the database.
These are the core tables that the database will have:
Customer: which will have email, username, password....
Customers_Session: Stores information about customer session in hash
Group: basically tells what permissions a customer will have
Category: the category type of a product
Product: information about a product such as name, and description...
Product_Price: Price info on products. This will store the different prices put for each product at various times.
Product_Variation: information about product images, and various colors or styles of a product.
Customer_Orders: What products a customer has ordered.
Customer_Reviews: Reviews made by customers on a product.
Reviewed Products: This table is created based on many to many relationship between the Product table and the Review Table.
Ordered products: This table is created based on the many to many relationship between the Product and the Orders Table.
Based on the above, I have come up with the sql code below:
--
-- Table structure for table `users`
--
CREATE TABLE IF NOT EXISTS `users` (
`id` int(11) NOT NULL AUTO_INCREMENT ,
`username` varchar(30) NOT NULL,
`password` varchar(64) NOT NULL,
`first_name` varchar(50) NOT NULL,
`last_name` varchar(50) NOT NULL,
`email` varchar(50) NOT NULL,
`address` varchar(320) NOT NULL,
`zip` mediumint(5) NOT NULL,
`salt` varchar(40) NOT NULL,
`joined` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP ON UPDATE CURRENT_TIMESTAMP,
`group` tinyint(1) NOT NULL,
`dob` date NOT NULL,
`pic_url` varchar(225) NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
--
--
-- Table structure for table `groups`
--
CREATE TABLE IF NOT EXISTS `groups` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`name` varchar(20) NOT NULL,
`permissions` text NOT NULL,
PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
--
-- This is for category table
--
CREATE TABLE IF NOT EXISTS `category`(
`category_id` tinyint(3) NOT NULL AUTO_INCREMENT,
`category_type` varchar(100) NOT NULL,
`category_description` varchar(160) NOT NULL,
PRIMARY KEY (`category_id`)
)ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
--
--
-- This is for product table
--
CREATE TABLE IF NOT EXISTS `products`(
`product_id` int(11) NOT NULL AUTO_INCREMENT,
`product_name` varchar(100) NOT NULL UNIQUE,
`product_description` varchar(160) NOT NULL,
`quantity` int(5) NOT NULL,
`product_code` varchar(4) NOT NULL,
`keywords` varchar(70) NOT NULL,
`category_id` tinyint(3),
PRIMARY KEY (`product_id`),
INDEX (`category_id`),
CONSTRAINT FOREIGN KEY (`category_id`) REFERENCES category(`category_id`) ON DELETE SET NULL
)ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
--
--
--
-- Table structure for table `bookings`
--
CREATE TABLE IF NOT EXISTS `bookings` (
`bookings_id` int(11) NOT NULL AUTO_INCREMENT,
`party_type` varchar(50) NOT NULL,
`location` varchar(100) NOT NULL,
`day` varchar(10) NOT NULL,
`time` smallint(6) NOT NULL,
`people_count` smallint(6) NOT NULL,
`booking_name` varchar(50) NOT NULL,
`booking_email` varchar(50) NOT NULL,
PRIMARY KEY (`bookings_id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='This is for the bookings' AUTO_INCREMENT=1 ;
--
-- Dumping data for table `groups`
--
INSERT INTO `groups` (`id`, `name`, `permissions`) VALUES
(1, 'Administrator', '{"admin":1}'),
(2, 'Users', '{"users":2}');
--
-- Table Structure for Reviews
--
CREATE TABLE IF NOT EXISTS `customer_reviews`(
`reviews_id` int(11) NOT NULL AUTO_INCREMENT,
`user_id` int(11),
`rating` int(5) NOT NULL,
`comment` varchar(160) NOT NULL,
PRIMARY KEY(`reviews_id`),
INDEX (`user_id`),
CONSTRAINT FOREIGN KEY(`user_id`) REFERENCES users(`user_id`) ON DELETE SET NULL
)ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
--
--
-- Table structure for reviewed products This is a many relationshi btw reviews table and product
--
CREATE TABLE IF NOT EXISTS `reviewed_products`(
`product_id` int(11),
`reviews_id`int(11),
PRIMARY KEY(`product_id`,`reviews_id`),
CONSTRAINT FOREIGN KEY(`product_id`) REFERENCES products(`product_id`) ON DELETE SET NULL,
CONSTRAINT FOREIGN KEY(`reviews_id`) REFERENCES customer_reviews(`reviews_id`) ON DELETE SET NULL
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='This is for many to many cardinality btw reviews and products' AUTO_INCREMENT=1 ;
--
--
-- Table structure for table `orders`
--
CREATE TABLE IF NOT EXISTS `customer_orders` (
`order_id` int(11) NOT NULL AUTO_INCREMENT,
`order_time` int(11) NOT NULL,
`amount` int(5),
`confirmation_number` int(,
`user_id` int(11),
`product_id` int(11),
PRIMARY KEY (`order_id`),
INDEX (`user_id`),
CONSTRAINT FOREIGN KEY (`user_id`) REFERENCES users(`user_id`) ON DELETE RESTRICT
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
/* We need a new table since the customer_order and product is in a many to many relationship */
--
--
-- Table structure for table `curtomer_order_product`
--
CREATE TABLE IF NOT EXISTS `ordered_product`(
`product_id` int(11),
`order_id` int(11),
`quantity` smallint(5),
PRIMARY KEY(`product_id`,`order_id`),
INDEX (`product_id`,`order_id`),
CONSTRAINT FOREIGN KEY (`order_id`) REFERENCES customer_orders(`order_id`) ON DELETE RESTRICT,
CONSTRAINT FOREIGN KEY (`product_id`) REFERENCES products(`product_id`) ON DELETE RESTRICT
)ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
--
-- This is for price table
--
CREATE TABLE IF NOT EXISTS `product_price`(
`price_id` int(11) NOT NULL AUTO_INCREMENT,
`price` decimal(6,2) NOT NULL,
`product_id` int(11) NOT NULL,
PRIMARY KEY (`price_id`),
INDEX (`product_id`),
CONSTRAINT FOREIGN KEY (`product_id`) REFERENCES products(`product_id`)
)ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
--
--
-- Table structure for table `product_variations`
--
CREATE TABLE IF NOT EXISTS `product_variations`(
`variations_id` int(11) NOT NULL AUTO_INCREMENT,
`color_name` varchar(10) NOT NULL,
`color_value` char(6) NOT NULL,
`product_id` int(11),
`picture1` varchar(100) NOT NULL,
`picture2` varchar(100) NOT NULL,
`picture3` varchar(100) NOT NULL,
PRIMARY KEY (`variations_id`),
INDEX (`product_id`),
CONSTRAINT FOREIGN KEY (`product_id`) REFERENCES products(`product_id`) ON DELETE RESTRICT
)ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
--
--
-- Table structure for table `users_session`
--
CREATE TABLE IF NOT EXISTS `users_session` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`user_id` int(11) NOT NULL,
`hash` varchar(64) NOT NULL,
PRIMARY KEY (`id`),
INDEX (`user_id`),
CONSTRAINT FOREIGN KEY(`user_id`) REFERENCES users(`user_id`) ON DELETE RESTRICT
) ENGINE=InnoDB DEFAULT CHARSET=latin1 AUTO_INCREMENT=1 ;
The problem is that when I try to run the above code in PHPmyadmin, I get an error stating "Cannot add foreign key constraint". This starts to happen when creating the customer_Reviews table and any other subsequent tables that require foreign keys.
My questions are:
1. Would you recommend designing the database this way.
2. Why am I getting the "Cannot add foreign key constraint" error?
Thanks.

Answer 1

For a full quality review of your database design, you might try the Code Review sister site. At a glance, I don't see any glaring issues with your database design or your SQL.
The foreign key constraint is failing because you have misnamed the column in question.
CONSTRAINT FOREIGN KEY(`user_id`) REFERENCES users(`user_id`)
should be:
CONSTRAINT FOREIGN KEY(`user_id`) REFERENCES users(`id`)