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MySQL - Alter Table
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In this article, we would like to show you how to modify a table in MySQL.
Quick solution:
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ALTER TABLE `table_name`2
ADD `column_name` DATA_TYPE;xxxxxxxxxx1
ALTER TABLE `table_name`2
MODIFY `column_name` DATA_TYPE;xxxxxxxxxx1
ALTER TABLE `table_name`2
DROP `column_name`;Note:
Go to the official documentation to see what you can use as
DATA_TYPE.
To show how the ALTER TABLE statement works, 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 add email column to the users table.
Query:
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ALTER TABLE `users`2
ADD `email` VARCHAR(255);Output (SELECT * FROM `users`):
In this example, we will delete the department_id column.
Query:
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ALTER TABLE `users`2
DROP `department_id`;Output (SELECT * FROM `users`):
In this example, we will modify salary column datatype from DECIMAL to VARCHAR.
Query:
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ALTER TABLE `users`2
MODIFY COLUMN `salary` VARCHAR(255);Output:
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
`department_id` INT(10) UNSIGNED,6
`salary` DECIMAL(15,2) NOT NULL,7
PRIMARY KEY (`id`)8
);insert_data.sql file:
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INSERT INTO `users`2
( `name`, `surname`, `department_id`, `salary`)3
VALUES4
('John', 'Stewart', 1, '3512.00'),5
('Chris', 'Brown', 2, '1344.00'),6
('Kate', 'Lewis', 3, '6574.00'),7
('Ailisa', 'Gomez', NULL, '6500.00'),8
('Gwendolyn', 'James', 2, '4200.00'),9
('Simon', 'Collins', 4, '3320.00'),10
('Taylor', 'Martin', 2, '1500.00'),11
('Andrew', 'Thompson', NULL, '2100.00');