Adding a Foreign Key to MariaDB / MySQL table - mysql

Question

I have 3 tables:
CREATE TABLE `channels` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`status` enum('active','inactive') NOT NULL DEFAULT 'active’,
`description` text DEFAULT NULL,
`created_at` timestamp NULL DEFAULT NULL,
`updated_at` timestamp NULL DEFAULT NULL,
`deleted_at` timestamp NULL DEFAULT NULL,
PRIMARY KEY (`id`),
) ENGINE=InnoDB AUTO_INCREMENT=485 DEFAULT CHARSET=utf8;
CREATE TABLE `categories` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(255) NOT NULL,
`content` text DEFAULT NULL,
`description` text DEFAULT NULL,
`status` enum('active','inactive') NOT NULL DEFAULT 'active',
`created_at` timestamp NOT NULL DEFAULT current_timestamp(),
`updated_at` timestamp NOT NULL DEFAULT current_timestamp() ON UPDATE current_timestamp(),
`deleted_at` timestamp NULL DEFAULT NULL,
PRIMARY KEY (`id`),
) ENGINE=InnoDB AUTO_INCREMENT=128 DEFAULT CHARSET=utf8;
CREATE TABLE `events` (
`id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`name` varchar(255) NOT NULL,
`content` text DEFAULT NULL,
`timezone` varchar(255) DEFAULT NULL,
`recurring` tinyint(1) NOT NULL DEFAULT 0,
`all_day` tinyint(1) NOT NULL DEFAULT 0,
`starts_at` timestamp NULL DEFAULT NULL,
`ends_at` timestamp NULL DEFAULT NULL,
`started_at` timestamp NULL DEFAULT NULL,
`completed_at` timestamp NULL DEFAULT NULL,
`status` enum('active','inactive','in_progress','complete') DEFAULT 'active',
`created_at` timestamp NULL DEFAULT NULL,
`updated_at` timestamp NULL DEFAULT NULL,
`deleted_at` timestamp NULL DEFAULT NULL,
PRIMARY KEY (`id`),
) ENGINE=InnoDB AUTO_INCREMENT=82 DEFAULT CHARSET=utf8;
I want to alter the events table to add more fields and add foreign keys to channel, event_type and client_event_type.
I've tried this:
alter table `events`
add `channel` int unsigned not null,
add `event_type` int unsigned not null,
add `client_event_type` int unsigned not null,
add constraint `events_channel_foreign` foreign key `channel` references `channels`(`id`),
add constraint `events_event_type_foreign` foreign key `event_type` references `categories`(`id`),
add constraint `events_clientEventType_foreign` foreign key `client_event_type` references `categories`(`id`),
It comes up with :
You have an error in your SQL syntax; check the manual that
corresponds to your MariaDB server version for the right syntax to use
near 'references channels(id), add constraint
events_event_type_foreign foreig' at line 5
What am I doing wrong?
Thanks

Answer 1

You're missing parantheses:
alter table `events`
add `channel` int unsigned not null,
add `event_type` int unsigned not null,
add `client_event_type` int unsigned not null,
add constraint `events_channel_foreign` foreign key (`channel`) references `channels`(`id`),
add constraint `events_event_type_foreign` foreign key (`event_type`) references `categories`(`id`),
add constraint `events_clientEventType_foreign` foreign key (`client_event_type`) references `categories`(`id`)