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MySQL - make column values unique

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In this article, we would like to show you how to make column values unique in MySQL.

Quick solution:

ALTER TABLE `table_name` 
ADD UNIQUE (`column_name`);

or

ALTER TABLE `table_name`
ADD CONSTRAINT `constraing_name` UNIQUE (`column1`, `column2`, `columnN`);

Practical example

To show how to make column values unique, we will use the following table:

MySQL - example data used to make column values unique
MySQL - example data used to make column values unique

Example 1 - make single column unique

In this example, we will make name column unique.

Query:

ALTER TABLE `users`
ADD CONSTRAINT `UC_username` UNIQUE (`name`);

Result:

Using query

SHOW INDEXES FROM `users`;
MySQL - make column value unique - result
MySQL - make column value unique - result

Using HeidiSQL

MySQL - make column value unique - result 
MySQL - make column value unique - result

Example 2 - make multiple columns unique

In this example, we will make name and country columns unique.

Query:

ALTER TABLE `users`
ADD CONSTRAINT `UC_user` UNIQUE (`name`, `country`);

Result:

Using query

SHOW INDEXES FROM `users`;
MySQL - make multiple column values unique - result
MySQL - make multiple column values unique - result 

Using HeidiSQL:

MySQL - make multiple column values unique - result
MySQL - make multiple column values unique - result 

MySQL - Problems

MySQL - make column values unique
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