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MySQL - count duplicated rows

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In this article, we would like to show you how to count duplicated rows in MySQL.

Quick solution:

SELECT 
    `column_name`, COUNT(`column_name`)
FROM
    `table_name`
GROUP BY 
    `column_name`
HAVING 
    (COUNT(`column_name`) > 1);

 

Practical example

To show how to count duplicated rows, we will use the following users table:

MySQL - example data used to count duplicated rows
MySQL - example data used to count duplicated rows

Note:

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

Example

In this example, we will count duplicated user names.

Query:

SELECT 
    `name`, COUNT(`name`) AS 'count'
FROM
    `users`
GROUP BY 
    `name`
HAVING 
    (COUNT(`name`) > 1);

Result:

MySQL - count duplicated rows - result
MySQL - count duplicated rows - result

Database preparation

create_tables.sql file:

CREATE TABLE `users` (
	`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,
	`name` VARCHAR(100) NOT NULL,
	`email` VARCHAR(100) NOT NULL,
	`country` VARCHAR(15) NOT NULL,
	PRIMARY KEY (`id`)
)
ENGINE=InnoDB;

insert_data.sql file:

INSERT INTO `users`
	(`name`, `email`, `country`)
VALUES
	('Tom', 'tom1@email.com', 'Poland'),
	('Tom', 'tom2@email.com', 'Poland'),
    ('Tom', 'tom3@email.com', 'Poland'),
    ('Kim', 'kim1@email.com', 'Vietnam'),
    ('Kim', 'kim2@email.com', 'Vietnam'),
    ('Chris', 'chris1@email.com', 'Spain'),
	('Chris', 'chris2@email.com', 'Spain'),
	('Chris', 'chris3@email.com', 'USA');

MySQL - Problems

MySQL - count duplicated rows
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