MySQL Error: 1452 - Cannot add or update a child row - mysql

Question

Error seems to occur when I try to INSERT into Items_Puchased (bottom lines). Ignore all comments.
Error Code: 1452. Cannot add or update a child row: a foreign key
constraint fails (shippingcontainers.items_purchased, CONSTRAINT
items_purchased_ibfk_2 FOREIGN KEY (container) REFERENCES stock
(container))
CREATE TABLE Customer (
customer_reference int UNIQUE AUTO_INCREMENT,
primary key (customer_reference),
forename VARCHAR(20),
surname VARCHAR(20),
contact VARCHAR(15),
email VARCHAR(50),
building VARCHAR(5),
road VARCHAR(40),
city VARCHAR(30),
postcode VARCHAR(7),
county VARCHAR(30));
CREATE TABLE Invoice (
invoice_reference int UNIQUE AUTO_INCREMENT,
customer_reference int UNIQUE,
primary key (invoice_reference),
foreign key (customer_reference) references Customer(customer_reference),
invoice_cost DECIMAL(20,2),
paid bit,
order_date DATETIME,
delivery_date DATE);
CREATE TABLE Stock (
container VARCHAR(10) UNIQUE NOT NULL DEFAULT 0,
primary key (container),
SBADNLon INT(4),
SBADNFel INT(4),
SBADNSou INT(4),
CHECK (container = ("SBADN-Lon" > 0, "SBADN-Fel" > 0, "SBADN-Sou" > 0)));
This is just showing 3 of the possible container variations
Each attribute stores a value containing the number of that model available in inventory
CREATE TABLE Items_Purchased (
container_ordered int UNIQUE AUTO_INCREMENT,
invoice_reference int,
container VARCHAR(10) NOT NULL DEFAULT "None",
container_cost decimal(20,2) NULL,
container_size VARCHAR(6) NOT NULL,
colour VARCHAR(5) NOT NULL,
grade CHAR(1) NOT NULL,
depot VARCHAR(15) NOT NULL,
container_type VARCHAR(20) NOT NULL,
conditionn VARCHAR(4) NOT NULL,
primary key (container_ordered, container_size, colour, grade, depot, container_type, conditionn));
foreign key (invoice_reference) references Invoice (invoice_reference),
foreign key (container) references Stock (container),
foreign key (container_size) references Container_Size (container_size),
foreign key (colour) references Colour (colour),
foreign key (grade) references Grade (grade),
foreign key (depot) references Depot (depot),
foreign key (container_type) references Container_Type (container_type),
foreign key (conditionn) references Conditionn (conditionn));
CREATE TABLE Depot (
depot VARCHAR(15) NOT NULL,
container_ordered int,
primary key (depot),
foreign key (container_ordered) references Items_Purchased(container_ordered),
CHECK (depot = ("london","felixstowe","southampton")));
CREATE TABLE Container_Type (
container_type VARCHAR(20) NOT NULL,
container_ordered int,
primary key (container_type),
foreign key (container_ordered) references Items_Purchased(container_ordered),
CHECK (container_type = ("dry","inslated","refreigerated","open top","tunnel")));
CREATE TABLE Container_Size (
container_size VARCHAR(6) NOT NULL,
container_ordered int,
primary key (container_size),
foreign key (container_ordered) references Items_Purchased(container_ordered),
CHECK (container_size = ("small","medium","large")));
CREATE TABLE Colour (
colour VARCHAR(5) NOT NULL,
container_ordered int,
primary key (colour),
foreign key (container_ordered) references Items_Purchased(container_ordered),
CHECK (colour = ("black","green")));
CREATE TABLE Conditionn (
conditionn VARCHAR(4) NOT NULL,
container_ordered int,
primary key (conditionn),
foreign key (container_ordered) references Items_Purchased(container_ordered),
CHECK (conditionn = ("new","used")));
CREATE TABLE Grade (
grade CHAR(1) NOT NULL,
container_ordered int,
primary key (grade),
foreign key (container_ordered) references Items_Purchased(container_ordered),
CHECK (grade = ("a","b","c")));
I am unsure on why I am getting this error code, can anyone assist? It occurs when adding
INSERT INTO Customer (
forename, surname, contact, email, building, road, city, postcode, county)
VALUES (
"james", "kelly", 07930317616, "james#uni.com", 123, "Yellow Road", "Ipswich", "IP11SQ", "Suffolk");
INSERT INTO Customer (
forename, surname, contact, email, building, road, city, postcode, county)
VALUES (
"ben", "smith", 0793031754, "ben#uni.com", 45, "Red Road", "Woodbridge", "IP142DD", "Suffolk");
INSERT INTO Invoice (
invoice_cost, paid, order_date, delivery_date)
VALUES (
1435.34, 1, 19/12/2017, 21/12/2017);
INSERT INTO Invoice (
invoice_cost, paid, order_date, delivery_date)
VALUES (
1035.12, 0, 02/02/2018, 29/12/2017);
INSERT INTO Stock (
SBADNLon, SBADNFel, SBADNSou)
VALUES (
3, 2, 1);
INSERT INTO Items_Purchased (
container_cost, container_size, colour, grade, depot, container_type, conditionn)
VALUES (
1645.21, "large", "black", "a", "london", "insulated", "new")

Answer 1

Look at your foreign key relationships with the Items_Purchased table. It sounds like you have a mismatch happening. And in looking at your table definition, you have a lot of foreign keys identified. This type of spider web construction is not typical and can cause you many problems. I would also take another look at your foreign keys and assess what the need is for each of them.

Answer 2

Your default value in table stock for column container is 0 and the default value for that column in the Items_Purchased table is "None".
As you don't assign any value for those columns in your insert statements, when you try to insert into the Items_Purchased table, it uses the default value for the column container "None" and this value doesn't exist in your stock table (the only value that exists it's 0).
You should make them the same value, or as default, in your Items_Purchased table set it as 0 like:
CREATE TABLE Items_Purchased (
container_ordered int UNIQUE AUTO_INCREMENT,
invoice_reference int,
container VARCHAR(10) NOT NULL DEFAULT 0,
container_cost decimal(20,2) NULL,
container_size VARCHAR(6) NOT NULL,
colour VARCHAR(5) NOT NULL,
grade CHAR(1) NOT NULL,
depot VARCHAR(15) NOT NULL,
container_type VARCHAR(20) NOT NULL,
conditionn VARCHAR(4) NOT NULL,
primary key (container_ordered, container_size, colour, grade, depot, container_type, conditionn));
foreign key (invoice_reference) references Invoice (invoice_reference),
foreign key (container) references Stock (container),
foreign key (container_size) references Container_Size (container_size),
foreign key (colour) references Colour (colour),
foreign key (grade) references Grade (grade),
foreign key (depot) references Depot (depot),
foreign key (container_type) references Container_Type (container_type),
foreign key (conditionn) references Conditionn (conditionn));