MySQL join multiple tables with foreign keys - mysql

Question

I stored my address information in several tables: country, zip, street and number.
CREATE TABLE country (
country_id INT,
name VARCHAR(45),
PRIMARY KEY(country_id));
CREATE TABLE zip (
zip_id INT,
zip VARCHAR(45),
PRIMARY KEY(zip_id));
CREATE TABLE street (
street_id INT,
name VARCHAR(45),
PRIMARY KEY(street_id));
CREATE TABLE number (
number_id INT,
number INT,
PRIMARY KEY(number_id));
I put the information together using an address table which contains the ids of the previously mentioned tables as foreign keys.
CREATE TABLE address (
address_id INT,
country_id INT,
zip_id INT,
street_id INT,
number_id INT,
PRIMARY KEY(address_id),
FOREIGN KEY(country_id) REFERENCES country(country_id),
FOREIGN KEY(zip_id) REFERENCES zip(zip_id),
FOREIGN KEY(street_id) REFERENCES street(street_id),
FOREIGN KEY(number_id) REFERENCES number(number_id));
How can I display a complete address with one SQL statement?

Answer 1

As mentioned in the comments first you need to add the id's from the other tables into the adress table. In the sql above you set the relation with foreign keys but the address table don't have any fields to map it to. You should create the address table like:
CREATE TABLE address (
address_id INT,
country_id INT,
zip_id INT,
street_id INT,
number_id INT,
PRIMARY KEY(address_id),
FOREIGN KEY(country_id) REFERENCES country(country_id),
FOREIGN KEY(zip_id) REFERENCES zip(zip_id),
FOREIGN KEY(street_id) REFERENCES street(street_id),
FOREIGN KEY(number_id) REFERENCES number(number_id));
Then you can make a join like:
SELECT a.address_id, c.name, s.name, n.number, z.zip
FROM address a
JOIN country c ON c.country_id = a.country_id
JOIN street s ON s.street_id = a.street_id
JOIN number n ON n.number_id = a.number_id
JOIN zip z ON z.zip_id = a.zip_id
But making a table for number (if you mean street number?) and zip might not be the best idea. Normally you want a table for countries but having a table for each zip instead of just adding them directly to the address table seems wrong. But I don't have all the info so you might have a good reason for it.