Getting a Cannot add Foreign Key Constraint MySQL

Question

I am having some trouble with phpMyAdmin and MySQL. All of the tables load just fine except for the order table. No matter if I do it all at once, or one table at a time, I get a #1215 - Cannot add foreign key constraint.

This happens for the Orders table only and the Customer_Number attribute. What in the world am I missing here. Thanks in advance.

-- phpMyAdmin SQL Dump
-- version 4.2.11
-- http://www.phpmyadmin.net
--
-- Host: 127.0.0.1
-- Generation Time: Apr 19, 2015 at 01:22 AM
-- Server version: 5.6.21
-- PHP Version: 5.6.3

SET SQL_MODE = "NO_AUTO_VALUE_ON_ZERO";
SET time_zone = "+00:00";
SET foreign_key_checks=0;

/*!40101 SET @OLD_CHARACTER_SET_CLIENT=@@CHARACTER_SET_CLIENT */;
/*!40101 SET @OLD_CHARACTER_SET_RESULTS=@@CHARACTER_SET_RESULTS */;
/*!40101 SET @OLD_COLLATION_CONNECTION=@@COLLATION_CONNECTION */;
/*!40101 SET NAMES utf8 */;


-- Database: `popcorn`


-- --------------------------------------------------------


-- Table structure for table `customer`


CREATE TABLE IF NOT EXISTS `customer` (
  `Scout_Number` int(10) NOT NULL,
  `Customer_Number` int(10) NOT NULL,
  `Fname` varchar(15) NOT NULL,
  `Lname` varchar(15) NOT NULL,
  `House_Number` int(7) NOT NULL,
  `Street` varchar(15) NOT NULL,
  `City` varchar(15) NOT NULL,
  `State` char(2) NOT NULL,
  `Zip` int(5) NOT NULL,
  `Phone` int(10) NOT NULL,
  `Email` varchar(30) NOT NULL,
  PRIMARY KEY (Scout_Number, Customer_Number)


) ENGINE=InnoDB DEFAULT CHARSET=latin1;

-- --------------------------------------------------------


-- Table structure for table `den`


CREATE TABLE IF NOT EXISTS `den` (
  `Den_Number` int(3) NOT NULL,
  `User_Name` varchar(8) NOT NULL,
  `Fname` varchar(15) NOT NULL,
  `Lname` varchar(15) NOT NULL,
  `Phone` int(10) NOT NULL,
  `Email` varchar(30) NOT NULL,
  `Den_City` varchar(15) NOT NULL,
  `Sales_Goal` int(10) NOT NULL,
  `Den_Sales_Total` decimal(10,2) NOT NULL,
  `Den_State` char(2) NOT NULL,
  PRIMARY KEY (Den_Number)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;


-- Dumping data for table `den`




-- Table structure for table `order`


CREATE TABLE IF NOT EXISTS `order` (
  `Order_Number` int(10) NOT NULL,
  `Customer_Number` int(10) NOT NULL,
  `Donation` decimal(5,2) NOT NULL,
  `Order_Total` decimal(5,2) NOT NULL,
  `Payment_Status` char(1) NOT NULL,
  `Payment_Type` varchar(10) NOT NULL,
  `Date` date NOT NULL,
  `Delivery_Status` char(1) NOT NULL,
  PRIMARY KEY (Order_Number),
  FOREIGN KEY (Customer_Number) REFERENCES customer(Customer_Number)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

-- --------------------------------------------------------


-- Table structure for table `order_product`


CREATE TABLE IF NOT EXISTS `order_product` (
  `Order_Number` int(10) NOT NULL,
  `Product_Number` int(10) NOT NULL,
  PRIMARY KEY (Order_Number, Product_Number)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

-- --------------------------------------------------------


-- Table structure for table `product`


CREATE TABLE IF NOT EXISTS `product` (
  `Product_Number` int(10) NOT NULL,
  `Product_Name` varchar(15) NOT NULL,
  `Description` text NOT NULL,
  `Image` blob NOT NULL,
  `Price` decimal(5,2) NOT NULL,
  PRIMARY KEY (Product_Number)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

-- --------------------------------------------------------


-- Table structure for table `scout`


CREATE TABLE IF NOT EXISTS `scout` (
  `Scout_Number` int(10) NOT NULL,
  `User_Name` char(8) NOT NULL,
  `Fname` varchar(15) NOT NULL,
  `Lname` varchar(15) NOT NULL,
  `Sales_Goal` decimal(10,2) NOT NULL,
  `Prize_Progress` int(10) NOT NULL,
  `Den_Number` int(3) NOT NULL,
  PRIMARY KEY (Scout_Number),
  FOREIGN KEY (Den_Number) REFERENCES den(Den_Number)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

/*!40101 SET CHARACTER_SET_CLIENT=@OLD_CHARACTER_SET_CLIENT */;
/*!40101 SET CHARACTER_SET_RESULTS=@OLD_CHARACTER_SET_RESULTS */;
/*!40101 SET COLLATION_CONNECTION=@OLD_COLLATION_CONNECTION */;

Answer 1

Columns referenced in a foreign key have to be indexed. You don't have an index on Customer_Number in the customer table. Either change the order of the columns in the composite primary key to customer table. Either change the order of the columns in the composite primary key to (Customer_Number, Scout_Number) or add an additional key just on the Customer_Number` column.

Note, however, that having a foreign key pointing to a non-unique column is a MySQL extension to SQL, and likely to be a bad idea. See Can a foreign key reference a non-unique index? . I wonder why the primary key of the customer table isn't just Customer_Number .