无法插入SQL脚本INSERT INTO值？

Question

I used a script to make a tables within the same database. Once both tables were made, I made a seperate script to insert a set of values in the table, however with one of the scripts it doesnt seem to insert any data into the table, but comes up with the error. These are my tables;

CREATE TABLE IF NOT EXISTS customers(
customer_id INT UNSIGNED NOT NULL,
first_name VARCHAR(20) NOT NULL,
middle_name VARCHAR(20),
last_name VARCHAR(40) NOT NULL,
email VARCHAR(60) NOT NULL,
password VARCHAR(40) NOT NULL,
dob DATETIME NOT NULL,
address_line VARCHAR(40) NOT NULL,
postcode VARCHAR(20) NOT NULL,
PRIMARY KEY(customer_id),
FOREIGN KEY(postcode) REFERENCE postcodes(postcode)
);

In a seperate script,

CREATE TABLE IF NOT EXISTS postcodes(
postcode VARCHAR(20) NOT NULL,
address_line_2 VARCHAR(20),
city VARCHAR(40) NOT NULL,
PRIMARY KEY(postcode)    
);

The scripts to insert data into the tables are here. This one works without any errors and successfully populates the table.

INSERT INTO postcodes(postcode,address_line_2,city)
Values
    ('DH1 568','Forest Lane','Durham'),
    ('DH1 679','Dry Wood','Durham'),
    ('DH1 4AS','North Of the Wall','Westeros'),
    ('DH1 4LA',"Snoop's Crib",'Durham');

And this is the one which comes up with an error message,

INSERT INTO customers(customer_id,first_name,postcode)
values
    ('1','Zaak','DH1 568'),
    ('2','Matt','DH1 679'),
    ('3','Jon','DH1 4AS'),
    ('4','Zak','DH1 4LA'),
    ('5','Gaz','DH1 7SO');

The error message which appears is,

ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`hardware_store`.`customers`, CONSTRAINT `customers_ibfk_1` FOREIGN KEY (`postcode`) REFER
ENCES `postcodes` (`postcode`))    

Answer 1

You have a foreign key constraint specifying that customers(postcode) refers to a valid postal code in the postcodes table.

Then, you try to insert 'DH1 7SO' and it doesn't work because this postcode is not in postcodes .

This is how foreign key references work. The database is working exactly as it should and doing exactly what you instructed it to do.

If you want the valid rows to be inserted and the invalid ones ignored, then use the IGNORE option on INSERT (see here ).