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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.
In MySQL we can create unique constraint for single or multiple columns.
Quick solution:
ALTER TABLE `table_name`
ADD UNIQUE (`column_name`);
or:
ALTER TABLE `table_name`
ADD CONSTRAINT `constraint_name` UNIQUE (`column_name`);
or:
ALTER TABLE `table_name`
ADD CONSTRAINT `constraint_name` UNIQUE (`column1`, `column2`, `columnN`);
Practical example
To show how to make column values unique, we will use the following table:
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`;
Using HeidiSQL
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`;
Using HeidiSQL:
