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MySQL - count distinct values
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In this article, we would like to show you how to count distinct values in MySQL.
Quick solution:
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SELECT COUNT(DISTINCT `column_name`)2
FROM `table_name`;xxxxxxxxxx1
SELECT COUNT(`column1`) AS `alias_name`, `column2`, `columnN`2
FROM `table_name`3
GROUP BY `columnN`4
ORDER BY COUNT(`column1`) DESC;To show how to count distinct 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 count the number of unique countries in users table.
Query:
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SELECT COUNT(DISTINCT(`country`)) AS `unique_countries`2
FROM `users`;Output:
In this example, we will count the number of users in every (unique) country in descending order.
Query:
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SELECT COUNT(`name`) AS `number of users`, `country`2
FROM `users`3
GROUP BY `country`4
ORDER BY COUNT(`name`) DESC;Output:
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
`country` VARCHAR(15) NOT NULL,5
PRIMARY KEY (`id`)6
)7
ENGINE=InnoDB;insert_data.sql file:
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INSERT INTO `users`2
(`name`, `country`)3
VALUES4
('Tom', 'Poland'),5
('Chris', 'Spain'),6
('Jack', 'Spain'),7
('Kim', 'Vietnam'),8
('Marco', 'Italy'),9
('Kate', 'Spain'),10
('Nam', 'Vietnam');