MySQL 5.6 Foreign Key Error Message - mysql

Question

I am getting this error when I try to run this bit of code in SQLFiddle. It is using MySQL 5.6.
Cannot add or update a child row: a foreign key constraint fails (db_9_f9acae.order_items, CONSTRAINT order_items_ibfk_1 FOREIGN KEY (Donut_Order_ID) REFERENCES custorder (Donut_Order_ID))
My code looks like this:
CREATE TABLE Customer (
Customer_ID INTEGER PRIMARY KEY AUTO_INCREMENT,
CustFirstName VARCHAR(50) NOT NULL,
CustLastName VARCHAR(50) NOT NULL,
Address VARCHAR(50) NOT NULL,
AptNum VARCHAR(50),
City VARCHAR(50) NOT NULL,
State VARCHAR(13) NOT NULL,
Zip VARCHAR(15) NOT NULL,
HomePhn VARCHAR(20),
MobPhn VARCHAR(20),
OthPhn VARCHAR(20)
);
CREATE TABLE Donut (
Donut_ID INTEGER PRIMARY KEY,
Donut_Name VARCHAR(255) NOT NULL,
Donut_Description VARCHAR(255) NOT NULL,
Donut_Price FLOAT NOT NULL
);
CREATE TABLE CustOrder (
Donut_Order_ID INTEGER PRIMARY KEY,
Date DATE NOT NULL,
Notes VARCHAR(255) NOT NULL,
Customer_ID INTEGER,
FOREIGN KEY (Customer_ID) REFERENCES Customer (Customer_ID)
);
CREATE TABLE Order_Items (
Donut_Order_ID INTEGER NOT NULL,
Donut_ID INTEGER NOT NULL,
Qty INTEGER NOT NULL,
PRIMARY KEY (Donut_Order_ID, Donut_ID),
FOREIGN KEY (Donut_Order_ID) REFERENCES CustOrder (Donut_Order_ID),
FOREIGN KEY (Donut_ID) REFERENCES Donut (Donut_ID)
);
CREATE VIEW CustInfo AS
SELECT CONCAT(CustFirstName,' ', CustLastName) AS CustFullName,
Customer_ID,
Address,
AptNum,
City,
State,
Zip,
HomePhn,
MobPhn,
OthPhn
FROM Customer;
CREATE INDEX DonutIndex ON Donut (Donut_Name);
INSERT INTO Customer VALUES
(1, "John", "Glenn", 1, NULL, "Kennedy Space Center", "FL", "32899", "[phone]", NULL, NULL),
(2, "Theodore", "Von Karman", "4800 Oak Dr", "Jet Propulsion Laboratory", "Pasadena", "CA", "91109", "[phone]", NULL, NULL),
(3, "Margaret", "Hamilton", "555 Technology Square", "Charles Stark Draper Laboratory", "Cambridge", "MA", "02139", "[phone]", "[phone]", NULL);
INSERT INTO Donut
VALUES
(1, 'Plain' , 'Plain Donut' , 1.50),
(2, 'Glazed' , 'Glazed Donut' , 1.75),
(3, 'Cinnamon' , 'Cinnamon Donut' , 1.75),
(4, 'Chocolate' , 'Chocolate Donut' , 1.75),
(5, 'Sprinkle' , 'Sprinkle Donut' , 1.75),
(6, 'Gluten-Free' , 'Gluten-Free Donut' , 2.00);
INSERT INTO Order_Items VALUES
(2 , 4 , 3),
(3, 2, 1);
INSERT INTO CustOrder VALUES
('1', '11-24-2017', NULL, '1'),
('2', '11-25-2017', NULL, '2');
This is my first time working with anything SQL related and have tried referring to the MySQL docs, but don't know what I'm doing wrong. The error does not appear until after the bottom 2 INSERT INTO statements are added. Any help would be greatly appreciated.

Answer 1

You are getting this error because you are trying to insert data set in table whose references are missing in referenced table for example in Order_Items you are trying to link custorder table with Donut_Order_ID 2 and 3 but it is empty
So first fill your custorder and then link with your table
INSERT INTO CustOrder VALUES
('1', '11-24-2017', NULL, '1'),
('2', '11-25-2017', NULL, '2');
INSERT INTO Order_Items VALUES
(2 , 4 , 3),
(3, 2, 1);
Also i see there is no reference present in CustOrder for Donut_Order_ID = 3 but in Order_Items data you have trying to link with this missing reference which will again give you error
demo