Can I alter a foreign key constraint in mysql?

Question

I have a foreign key in 3 tables and they are on cascade update . so I would like to add another cascade delete ,. Is that possible without dropping the constraint ? if yes please give me any example with alter .

Answer 1

To change your foreign key, you first have to drop it (using the name) and then create a new foreign key with the correct definition and your done!

ALTER TABLE `pets` DROP FOREIGN KEY `your_fk_name_here`;
ALTER TABLE `pets` ADD FOREIGN KEY (`owner_id`) REFERENCES `owners`(`id`) ON UPDATE CASCADE ON DELETE CASCADE;
or
ALTER TABLE `pets` ADD CONSTRAINT fk_owner_pet FOREIGN KEY (`owner_id`) REFERENCES `owners`(`id`) ON UPDATE CASCADE ON DELETE CASCADE;