Foreign Key Constraints In MySQL DB Gives Error - mysql

Question

am trying to implement a foreign key constraint but the mysql keeps giving me an error There are two tables "groups" table and "members" table.I have a many to many relationship between these tables and therefore used a third table called "members_groups" table for the many to many relationship. Note: "groups" and "members" tables have been created and contain data but I now want to add the "members_groups" table. Below are the sql codes:
Below is the script for the members table.
CREATE TABLE IF NOT EXISTS `members` (
`member_id` int(11) NOT NULL AUTO_INCREMENT,
`username` varchar(30) NOT NULL,
`email` varchar(50) NOT NULL,
`password` char(128) NOT NULL,
`salt` char(128) NOT NULL,
`group_id` bigint(64) unsigned NOT NULL,
`perm_override_add` bigint(64) unsigned NOT NULL,
`perm_override_remove` bigint(64) unsigned NOT NULL,
PRIMARY KEY (`member_id`),
KEY `member_id` (`member_id`)
) ENGINE=InnoDB;
script for the groups table
CREATE TABLE IF NOT EXISTS `groups` (
`group_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
`group_name` varchar(50) NOT NULL,
`permission` int(10) unsigned DEFAULT NULL,
PRIMARY KEY (`group_id`)
) ENGINE=InnoDB
script for the members_groups table
CREATE TABLE members_groups
(
member_id INT(11) NOT NULL ,
group_id INT(10) NOT NULL ,
PRIMARY KEY (member_id, group_id),
FOREIGN KEY (member_id) REFERENCES members(member_id) ON UPDATE CASCADE,
FOREIGN KEY (group_id) REFERENCES groups(group_id) ON UPDATE CASCADE
) ENGINE = InnoDB
This is the error I get from the mysql admin console.
Thanks.

Answer 1

You need to make the type same in your table. In your groups table you have defined
`group_id` int(10) unsigned NOT NULL AUTO_INCREMENT,
whereas in your members_groups table it is
group_id INT(10) NOT NULL ,
Try to make the change like
CREATE TABLE members_groups
(
member_id INT(11) NOT NULL ,
group_id INT(10) unsigned NOT NULL , --The datatype should be same as group_id in `groups` table
PRIMARY KEY (member_id, group_id),
FOREIGN KEY (member_id) REFERENCES members(member_id) ON UPDATE CASCADE,
FOREIGN KEY (group_id) REFERENCES `groups`(group_id) ON UPDATE CASCADE
) ENGINE = InnoDB;
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