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MySQL - find duplicated values
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In this article, we would like to show you how to find duplicated values in MySQL.
Quick solution:
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SELECT `column_name`, COUNT(`column_name`)2
FROM `table_name`3
GROUP BY `column_name`4
HAVING COUNT(`column_name`) > 1;To show how to find duplicated values, we will use the following table:
Note:
At the end of this article you can find database preparation SQL queries.
In this example, we will display the number of names that are duplicated in users table.
Query:
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SELECT `name`, COUNT(`name`) AS 'name_number'2
FROM `users`3
GROUP BY `name`4
HAVING COUNT(`name`) > 1;Result:
create_tables.sql file:
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CREATE TABLE `users` (2
`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,3
`name` VARCHAR(100) NOT NULL,4
`email` VARCHAR(100) NOT NULL,5
`country` VARCHAR(15) NOT NULL,6
PRIMARY KEY (`id`)7
)8
ENGINE=InnoDB;insert_data.sql file:
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INSERT INTO `users`2
(`name`, `email`, `country`)3
VALUES4
('Tom', 'tom1@email.com', 'Poland'),5
('Tom', 'tom2@email.com', 'Poland'),6
('Tom', 'tom3@email.com', 'Poland'),7
('Kim', 'kim1@email.com', 'Vietnam'),8
('Kim', 'kim2@email.com', 'Vietnam'),9
('Chris', 'chris1@email.com', 'Spain'),10
('Chris', 'chris2@email.com', 'Spain'),11
('Chris', 'chris3@email.com', 'USA');