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MySQL - Select from multiple tables (using JOIN)

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In this article, we would like to show you how to select from multiple tables using JOIN clause in MySQL.

Quick solution:

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

Practical example

To show how to count rows per day, we will use the following tables:

groups table:

MySQL - example data used to select from multiple tables
MySQL - example data used to select from multiple tables

users table:

MySQL - example data used to select from multiple tables
MySQL - example data used to select from multiple tables

Note:

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

Example

In this example, we will display the following columns from users table:

  • id,
  • username,
  • group_id,

and the following column from groups table:

  • group_name

We will use aliases:

  • u - for users┬átable,
  • g - for groups table.

In our example group_id is a reference column for `groups`.`id` (g.`id`). 

Query:

SELECT u.`id`, u.`username`, u.`group_id`, g.`group_name`
FROM `users` AS u
JOIN `groups` AS g ON u.`group_id` = g.`id`;

Result:

MySQL - select from multiple tables using JOIN - result
MySQL - select from multiple tables using JOIN - result

Database preparation

create_tables.sql file:

CREATE TABLE `groups` (
	`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
	`group_name` VARCHAR(50) NOT NULL,
	PRIMARY KEY (`id`)
);

CREATE TABLE `users` (
	`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
	`username` VARCHAR(50) NOT NULL,
	`group_id` INT(10) UNSIGNED,
	PRIMARY KEY (`id`),
	FOREIGN KEY (`group_id`) REFERENCES `groups`(`id`)
);

insert_data.sql file:

INSERT INTO `groups`
	(`group_name`)
VALUES
	('Group_One'),
	('Group_Two'),
	('Group_Three');

INSERT INTO `users`
	(`username`, `group_id`)
VALUES
	('Tom', 1),
	('Kate', 2),
	('Ann', 3),
	('Jack', 2),
	('Kim', 1);

MySQL - Problems

MySQL - Select from multiple tables (using JOIN)
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