MySQL - Left Join

In this article, we would like to show you how to use LEFT JOIN in MySQL.

Quick solution:

SELECT `column1`, `column2`, `columnN`
FROM `table1`
LEFT JOIN `table2`
ON `table1`.`column_name` = `table2`.`column_name`;

Practical example

To show how the LEFT JOIN works, we will use the following tables:

Note:

At the end of this article you can find databases preparation SQL queries.

Example 

In this example, we will select all users with department information.

Query:

SELECT * FROM `users`
LEFT JOIN `departments` 
ON `departments`.`id` = `users`.`department_id`;

Output:

Database preparation

create_tables.sql file:

CREATE TABLE `departments` (
	`id` INT(10) UNSIGNED NOT NULL,
	`department_name` VARCHAR(50) NOT NULL,
	`location` VARCHAR(50) NULL,
	PRIMARY KEY (`id`)
);

CREATE TABLE `users` (
	`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
	`name` VARCHAR(50) NOT NULL,
	`surname` VARCHAR(50) NOT NULL,
	`department_id` INT(10) UNSIGNED,
	PRIMARY KEY (`id`),
	FOREIGN KEY (`department_id`) REFERENCES `departments` (`id`)
)

insert_data.sql file:

INSERT INTO `departments`
	(`id`, `department_name`, `location`)
VALUES
	(1, 'Sales', 'New York'),
	(2, 'Finance', NULL),
	(3, 'HR', 'Atlanta'),
	(4, 'Purchase', 'New Orlean'),
	(5, 'Operations', 'Boston');

INSERT INTO `users`
	( `name`, `surname`, `department_id`)
VALUES
	('John', 'Stewart', 1),
	('Chris', 'Brown', 2),
	('Kate', 'Lewis', 3),
	('Ailisa', 'Gomez', NULL),
	('Gwendolyn', 'James', 2),
	('Simon', 'Collins', 4),
	('Taylor', 'Martin', 2),
	('Andrew', 'Thompson', NULL);