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MySQL - add index to existing table using ALTER TABLE
3 points
In this article, we would like to show you how to add index to an existing table in MySQL.
Quick solution:
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ALTER TABLE `table_name` 2
ADD INDEX `index_name` (`column2`, `column2`, `columnN`);To show how to add index to existing table using ALTER TABLE, 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 create an index for the salary column in users table.
Query:
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ALTER TABLE `users` 2
ADD INDEX `index_salary` (`salary`);Result:
1. Using query
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SHOW INDEX FROM `users` FROM `dirask`; -- where users-table_name, dirask-database_name
2. Using HeidiSQL
In this example, we will create an index on two columns using ALTER TABLE statement.
Query:
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ALTER TABLE `users` 2
ADD INDEX `index_full_name` (`name`, `surname`);Result:
1. Using query
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SHOW INDEX FROM `users` FROM `dirask`; -- where users-table_name, dirask-database_name
2. Using HeidiSQL
create_tables.sql file:
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CREATE TABLE `users` (2
`id` INT(10) UNSIGNED NOT NULL AUTO_INCREMENT,3
`name` VARCHAR(50) NOT NULL,4
`surname` VARCHAR(50) NOT NULL,5
`salary` DECIMAL(15,2) NOT NULL,6
PRIMARY KEY (`id`)7
);insert_data.sql file:
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INSERT INTO `users`2
( `name`, `surname`, `salary`)3
VALUES4
('John', 'Stewart', '3512.00'),5
('Chris', 'Brown', '1344.00'),6
('Kate', 'Lewis', '6574.00'),7
('Ailisa', 'Gomez', '6500.00'),8
('Gwendolyn', 'James', '4200.00'),9
('Simon', 'Collins', '3320.00'),10
('Taylor', 'Martin', '1500.00'),11
('Andrew', 'Thompson', '2100.00');