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MySQL - find duplicated values in multiple columns
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In this article, we would like to show you how to find duplicated values in multiple columns in MySQL.
Quick solution:
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SELECT 2
`column1`, COUNT(`column1`),3
`column2`, COUNT(`column2`),4
`columnN`, COUNT(`columnN`)5
FROM6
`table_name`7
GROUP BY 8
`column1`,9
`column2`,10
`columnN`11
HAVING 12
(COUNT(`column1`) > 1) AND 13
(COUNT(`column2`) > 1) AND14
(COUNT(`columnN`) > 1);To show how to find duplicated values in multiple columns, 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 duplicated users and countries where:
name_quantity- number of duplicated names,country_quantity- number of duplicated countries.
Note:
This works only when both
nameandcountryin a row are duplicated.
Query:
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SELECT 2
`name`, COUNT(`name`) AS 'name_quantity',3
`country`, COUNT(`country`) AS 'country_quantity'4
FROM5
`users`6
GROUP BY 7
`name`,8
`country`9
HAVING 10
(COUNT(`name`) > 1) AND 11
(COUNT(`country`) > 1);Result:
Note:
Notice that
Chrisuser bothname_quantityandcountry_quantityequals2because one user is from a different country.
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');