Question

The idea is quite simple: i have three (or more) tables

- master_tbl (id, something, somethingelse)
- tbl2 (id, ....)
- tbl3 (id, ....)

Now what i want is a foreign key relationship, such as tbl3.id would point to tbl2.id and tbl2.id would point to master_tbl.id – all foreign keys are ON UPDATE CASCADE and ON DELETE CASCADE. What I’ll get from this is that when I delete a record from tbl2, its tbl3 equivalent will get erased as well, but not master_tbl. When I delete a record from master_tbl, all three tables get erased.

When I try to create the foreign key on tbl3.id->tbl2.id, I get mysql error 150 – can’t create table (the tbl2.id->master_tbl.id is already created).
My MySQL version is 5.1.46. Any ideas why this might be?

EDIT: table definitions
smf_members aka master_table

-- Table "smf_members" DDL

CREATE TABLE `smf_members` (
  `id_member` mediumint(8) unsigned NOT NULL AUTO_INCREMENT,
  `member_name` varchar(80) NOT NULL DEFAULT '',
  `date_registered` int(10) unsigned NOT NULL DEFAULT '0',
  `posts` mediumint(8) unsigned NOT NULL DEFAULT '0',
  `id_group` smallint(5) unsigned NOT NULL DEFAULT '0',
  `lngfile` varchar(255) NOT NULL DEFAULT '',
  `last_login` int(10) unsigned NOT NULL DEFAULT '0',
  `real_name` varchar(255) NOT NULL DEFAULT '',
  `instant_messages` smallint(5) NOT NULL DEFAULT '0',
  `unread_messages` smallint(5) NOT NULL DEFAULT '0',
  `new_pm` tinyint(3) unsigned NOT NULL DEFAULT '0',
  `buddy_list` text NOT NULL,
  `pm_ignore_list` varchar(255) NOT NULL DEFAULT '',
  `pm_prefs` mediumint(8) NOT NULL DEFAULT '0',
  `mod_prefs` varchar(20) NOT NULL DEFAULT '',
  `message_labels` text NOT NULL,
  `passwd` varchar(64) NOT NULL DEFAULT '',
  `openid_uri` text NOT NULL,
  `email_address` varchar(255) NOT NULL DEFAULT '',
  `personal_text` varchar(255) NOT NULL DEFAULT '',
  `gender` tinyint(4) unsigned NOT NULL DEFAULT '0',
  `birthdate` date NOT NULL DEFAULT '0001-01-01',
  `website_title` varchar(255) NOT NULL DEFAULT '',
  `website_url` varchar(255) NOT NULL DEFAULT '',
  `location` varchar(255) NOT NULL DEFAULT '',
  `icq` varchar(255) NOT NULL DEFAULT '',
  `aim` varchar(255) NOT NULL DEFAULT '',
  `yim` varchar(32) NOT NULL DEFAULT '',
  `msn` varchar(255) NOT NULL DEFAULT '',
  `hide_email` tinyint(4) NOT NULL DEFAULT '0',
  `show_online` tinyint(4) NOT NULL DEFAULT '1',
  `time_format` varchar(80) NOT NULL DEFAULT '',
  `signature` text NOT NULL,
  `time_offset` float NOT NULL DEFAULT '0',
  `avatar` varchar(255) NOT NULL DEFAULT '',
  `pm_email_notify` tinyint(4) NOT NULL DEFAULT '0',
  `karma_bad` smallint(5) unsigned NOT NULL DEFAULT '0',
  `karma_good` smallint(5) unsigned NOT NULL DEFAULT '0',
  `usertitle` varchar(255) NOT NULL DEFAULT '',
  `notify_announcements` tinyint(4) NOT NULL DEFAULT '1',
  `notify_regularity` tinyint(4) NOT NULL DEFAULT '1',
  `notify_send_body` tinyint(4) NOT NULL DEFAULT '0',
  `notify_types` tinyint(4) NOT NULL DEFAULT '2',
  `member_ip` varchar(255) NOT NULL DEFAULT '',
  `member_ip2` varchar(255) NOT NULL DEFAULT '',
  `secret_question` varchar(255) NOT NULL DEFAULT '',
  `secret_answer` varchar(64) NOT NULL DEFAULT '',
  `id_theme` tinyint(4) unsigned NOT NULL DEFAULT '0',
  `is_activated` tinyint(3) unsigned NOT NULL DEFAULT '1',
  `validation_code` varchar(10) NOT NULL DEFAULT '',
  `id_msg_last_visit` int(10) unsigned NOT NULL DEFAULT '0',
  `additional_groups` varchar(255) NOT NULL DEFAULT '',
  `smiley_set` varchar(48) NOT NULL DEFAULT '',
  `id_post_group` smallint(5) unsigned NOT NULL DEFAULT '0',
  `total_time_logged_in` int(10) unsigned NOT NULL DEFAULT '0',
  `password_salt` varchar(255) NOT NULL DEFAULT '',
  `ignore_boards` text NOT NULL,
  `warning` tinyint(4) NOT NULL DEFAULT '0',
  `passwd_flood` varchar(12) NOT NULL DEFAULT '',
  `pm_receive_from` tinyint(4) unsigned NOT NULL DEFAULT '1',
  PRIMARY KEY (`id_member`),
  KEY `member_name` (`member_name`),
  KEY `real_name` (`real_name`),
  KEY `date_registered` (`date_registered`),
  KEY `id_group` (`id_group`),
  KEY `birthdate` (`birthdate`),
  KEY `posts` (`posts`),
  KEY `last_login` (`last_login`),
  KEY `lngfile` (`lngfile`(30)),
  KEY `id_post_group` (`id_post_group`),
  KEY `warning` (`warning`),
  KEY `total_time_logged_in` (`total_time_logged_in`),
  KEY `id_theme` (`id_theme`)
) ENGINE=InnoDB AUTO_INCREMENT=73 DEFAULT CHARSET=utf8;

cyp_users aka tbl2

-- Table "cyp_users" DDL

CREATE TABLE `cyp_users` (
  `id` mediumint(8) unsigned NOT NULL,
  `role` varchar(255) NOT NULL DEFAULT 'unregistered',
  PRIMARY KEY (`id`),
  CONSTRAINT `cyp_users_ibfk_1` FOREIGN KEY (`id`) REFERENCES `smf_members` (`id_member`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

cyp_vip_users aka tbl3

-- Table "cyp_vip_users" DDL

CREATE TABLE `cyp_vip_users` (
  `id` mediumint(8) NOT NULL,
  `od` date NOT NULL,
  `do` date NOT NULL,
  PRIMARY KEY (`id`)
) ENGINE=InnoDB DEFAULT CHARSET=latin1;

Answer 1

The ID's of tbl2 and tbl3 are different types.
Foreign Keys need to be of the same type.

• tbl2.ID is UNSIGNED
• tbl3.ID is SIGNED