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I need to add composite foreign key to table which structure looks like
CREATE TABLE IF NOT EXISTS `discount_month_devices` (
`id` int(10) UNSIGNED NOT NULL AUTO_INCREMENT,
`discount_month_id` int(11) UNSIGNED NOT NULL,
`global_device_id` int(11) DEFAULT NULL,
`location_id` int(11) UNSIGNED DEFAULT NULL,
`server_id` varchar(20) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `discount_month_id` (`discount_month_id`),
KEY `global_device_id` (`global_device_id`),
KEY `location_id` (`location_id`,`server_id`),
KEY `server_id` (`server_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4;
Devices table DDL looks like
CREATE TABLE IF NOT EXISTS `devices` (
`id` int(11) NOT NULL AUTO_INCREMENT,
`server_id` varchar(20) CHARACTER SET utf8mb4 NOT NULL,
`device_id` int(11) DEFAULT NULL,
`location_id` int(11) UNSIGNED DEFAULT NULL,
`device_lat` float DEFAULT NULL,
`device_long` float DEFAULT NULL,
....
PRIMARY KEY (`id`) USING BTREE,
UNIQUE KEY `devices_idx1` (`server_id`,`device_id`) USING BTREE,
KEY `devices_idx5` (`server_id`) USING BTREE,
KEY `devices_idx6` (`device_id`) USING BTREE,
KEY `devices_idx8` (`server_id`,`owner_id`) USING BTREE,
KEY `server_id` (`server_id`,`location_id`),
KEY `devices_idx14` (`location_id`)
) ENGINE=InnoDB AUTO_INCREMENT=1583586 DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci ROW_FORMAT=DYNAMIC;
ALTER TABLE `devices`
ADD CONSTRAINT `devices_fk1` FOREIGN KEY (`server_id`,`location_id`) REFERENCES `locations` (`server_id`, `location_id`) ON DELETE CASCADE ON UPDATE CASCADE,
ADD CONSTRAINT `devices_fk2` FOREIGN KEY (`discount_month_id`) REFERENCES `discount_month` (`id`);
There are location_id composite index. I can create FK for location_id and server_id separately so columns types and ranges should be right.
I would like to run alter table which should add the foreign which looks like
ALTER TABLE `discount_month_devices` ADD CONSTRAINT `discount_month_devices_fk3`
FOREIGN KEY (`location_id`, `server_id`) REFERENCES `devices`(`location_id`, `server_id`)
ON DELETE CASCADE ON UPDATE CASCADE;
This throws me an error: General error: 1215 Cannot add foreign key constraint
Does anybody know what could be the problem.
You must list the columns in the foreign key constraint in the same order that they appear in a key in the referenced table. Your key in devices is on (server_id, location_id) but you tried to reference them in your foreign key constraint as (location_id, server_id).
Try this:
ALTER TABLE `discount_month_devices`
ADD CONSTRAINT `discount_month_devices_fk3`
FOREIGN KEY (`server_id`, `location_id`)
REFERENCES `devices`(`server_id`, `location_id`)
ON DELETE CASCADE ON UPDATE CASCADE;
The order of columns in keys and constraints is not required to match the order of columns in the table definition.
TL;DR
We've seen on a virtual machine, that adding a UNIQUE index causes an older non-UNIQUE index to be removed automatically.
I cannot reproduce this on any other machines (yet?), and if I do:
mysql -e 'create db2'
mysqldump db1 | mysql db2
before adding the new index to db1, and then try adding the index on db2 instead, the old index is not removed from db2. Funky!
We have a snapshot of the machine with db1, and can reproduce it there in the existing db1 database...
Anybody have any idea what is going on? We have scripts to automate adding/removing indexes, and that started failing because on that one machine, the old index didn't exist any longer.
When a dump/restore cycle causes the problem to go away, that makes it hard understand, reproduce and reduce the problem to a simple example.
Details
The table in question looked like this before adding the new index (from SHOW CREATE TABLE). Note the monitoredTableRowID KEY:
CREATE TABLE `cfgAttributeInstances` (
`ID` int(10) unsigned NOT NULL AUTO_INCREMENT,
`attributeID` int(10) unsigned DEFAULT NULL,
`nodeID` int(10) unsigned DEFAULT NULL,
`groupID` int(10) unsigned DEFAULT NULL,
`statisticID` int(10) unsigned DEFAULT NULL,
`nodeStatisticID` int(10) unsigned DEFAULT NULL,
`serviceID` int(10) unsigned DEFAULT NULL,
`nodeServiceID` int(10) unsigned DEFAULT NULL,
`nodeComponentID` int(10) unsigned DEFAULT NULL,
`syslogFilterID` int(10) unsigned DEFAULT NULL,
`value` varchar(255) NOT NULL DEFAULT '',
PRIMARY KEY (`ID`),
UNIQUE KEY `nodeID` (`nodeID`,`attributeID`),
UNIQUE KEY `groupID` (`groupID`,`attributeID`),
UNIQUE KEY `statisticID` (`statisticID`,`attributeID`),
UNIQUE KEY `nodeStatisticID` (`nodeStatisticID`,`attributeID`),
UNIQUE KEY `serviceID` (`serviceID`,`attributeID`),
UNIQUE KEY `nodeServiceID` (`nodeServiceID`,`attributeID`),
KEY `attributeID` (`attributeID`),
KEY `monitoredTableRowID` (`nodeComponentID`),
KEY `syslogFilterID` (`syslogFilterID`),
CONSTRAINT `cfgAttributeInstances_ibfk_1` FOREIGN KEY (`attributeID`) REFERENCES `cfgAttributes` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_2` FOREIGN KEY (`nodeID`) REFERENCES `cfgNodes` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_3` FOREIGN KEY (`groupID`) REFERENCES `cfgGroups` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_4` FOREIGN KEY (`statisticID`) REFERENCES `cfgStatistics` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_5` FOREIGN KEY (`nodeStatisticID`) REFERENCES `cfgNodeStatistics` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_6` FOREIGN KEY (`serviceID`) REFERENCES `cfgServices` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_7` FOREIGN KEY (`nodeServiceID`) REFERENCES `cfgNodeServices` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_8` FOREIGN KEY (`nodeComponentID`) REFERENCES `cfgNodeComponents` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_9` FOREIGN KEY (`syslogFilterID`) REFERENCES `cfgSyslogFilters` (`ID`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='CapMon Attribute instances';
I added this index:
ALTER TABLE cfgAttributeInstances ADD
UNIQUE new_nodeComponentID (nodeComponentID, attributeID)
It looked like this after adding that index:
CREATE TABLE `cfgAttributeInstances` (
`ID` int(10) unsigned NOT NULL AUTO_INCREMENT,
`attributeID` int(10) unsigned DEFAULT NULL,
`nodeID` int(10) unsigned DEFAULT NULL,
`groupID` int(10) unsigned DEFAULT NULL,
`statisticID` int(10) unsigned DEFAULT NULL,
`nodeStatisticID` int(10) unsigned DEFAULT NULL,
`serviceID` int(10) unsigned DEFAULT NULL,
`nodeServiceID` int(10) unsigned DEFAULT NULL,
`nodeComponentID` int(10) unsigned DEFAULT NULL,
`syslogFilterID` int(10) unsigned DEFAULT NULL,
`value` varchar(255) NOT NULL DEFAULT '',
PRIMARY KEY (`ID`),
UNIQUE KEY `nodeID` (`nodeID`,`attributeID`),
UNIQUE KEY `groupID` (`groupID`,`attributeID`),
UNIQUE KEY `statisticID` (`statisticID`,`attributeID`),
UNIQUE KEY `nodeStatisticID` (`nodeStatisticID`,`attributeID`),
UNIQUE KEY `serviceID` (`serviceID`,`attributeID`),
UNIQUE KEY `nodeServiceID` (`nodeServiceID`,`attributeID`),
UNIQUE KEY `new_nodeComponentID` (`nodeComponentID`,`attributeID`),
KEY `attributeID` (`attributeID`),
KEY `syslogFilterID` (`syslogFilterID`),
CONSTRAINT `cfgAttributeInstances_ibfk_1` FOREIGN KEY (`attributeID`) REFERENCES `cfgAttributes` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_2` FOREIGN KEY (`nodeID`) REFERENCES `cfgNodes` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_3` FOREIGN KEY (`groupID`) REFERENCES `cfgGroups` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_4` FOREIGN KEY (`statisticID`) REFERENCES `cfgStatistics` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_5` FOREIGN KEY (`nodeStatisticID`) REFERENCES `cfgNodeStatistics` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_6` FOREIGN KEY (`serviceID`) REFERENCES `cfgServices` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_7` FOREIGN KEY (`nodeServiceID`) REFERENCES `cfgNodeServices` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_8` FOREIGN KEY (`nodeComponentID`) REFERENCES `cfgNodeComponents` (`ID`) ON DELETE CASCADE,
CONSTRAINT `cfgAttributeInstances_ibfk_9` FOREIGN KEY (`syslogFilterID`) REFERENCES `cfgSyslogFilters` (`ID`) ON DELETE CASCADE
) ENGINE=InnoDB DEFAULT CHARSET=latin1 COMMENT='CapMon Attribute instances';
But hey! Where did the monitoredTableRowID index go?
Again, I cannot reproduce this. If I do a mysqldump > dump.db/mysql < dump.db cycle, the monitoredTableRowID doesn't disappear...
Any ideas on what is going on?
The composite key with nodeComponentID causes the non-composite key with nodeComponentID to be redundant within the context of the foreign key reference it is used. MySQL automatically drops the redundant implicit index. The behavior is dependant on column index ordering, as the dropped index will always be the first column within the defined composite key. [sic]
The issue(s) are specifically caused by the automatic implicit index created when adding a foreign key CONSTRAINT, and the index(es) being explicitly defined in SHOW CREATE TABLE which is also used by mysqldump.
The index_name value is ignored if there is already an explicitly
defined index on the child table that can support the foreign key.
Otherwise, MySQL implicitly creates a foreign key index... [sic]
MySQL requires indexes on foreign keys and referenced keys so that
foreign key checks can be fast and not require a table scan. In the
referencing table, there must be an index where the foreign key
columns are listed as the first columns in the same order. Such an
index is created on the referencing table automatically if it does not
exist. This index might be silently dropped later, if you create
another index that can be used to enforce the foreign key constraint.
index_name, if given, is used as described previously. [sic]
To reproduce the issue
Implicit Key Example db-fiddle
Note - INDEX FK_BAR_FOO (foo_id) is not explicitly defined.
DROP TABLE IF EXISTS `BAR`;
DROP TABLE IF EXISTS `FOO`;
CREATE TABLE `FOO` (
`id` INT(11) NOT NULL,
PRIMARY KEY (`id`)
)
ENGINE=InnoDB
;
CREATE TABLE `BAR` (
`id` INT(11) NOT NULL,
`foo_id` INT(11) NOT NULL,
`b` INT(11) NOT NULL,
PRIMARY KEY (`id`),
CONSTRAINT `FK_BAR_FOO` FOREIGN KEY (`foo_id`) REFERENCES `FOO` (`id`) ON DELETE CASCADE
)
ENGINE=InnoDB
;
SHOW CREATE TABLE `BAR`;
Result
INDEX FK_BAR_FOO (foo_id) is explicitly defined in SHOW CREATE TABLE, but is implicitly created by MySQL.
CREATE TABLE `BAR` (
`id` INT(11) NOT NULL,
`foo_id` INT(11) NOT NULL,
`b` INT(11) NOT NULL,
PRIMARY KEY (`id`),
INDEX `FK_BAR_FOO` (`foo_id`),
CONSTRAINT `FK_BAR_FOO` FOREIGN KEY (`foo_id`) REFERENCES `FOO` (`id`) ON DELETE CASCADE
)
ENGINE=InnoDB
;
Composite Key Example: db-fiddle
ALTER TABLE `BAR`
ADD UNIQUE INDEX `foo_id_b` (`foo_id`, `b`);
SHOW CREATE TABLE `BAR`;
Result
foo_id index is removed due to being redundant.
Since foo_id is the first column within the composite key, the implicit foo_id index FK_BAR_FOO is removed.
CREATE TABLE `BAR` (
`id` INT(11) NOT NULL,
`foo_id` INT(11) NOT NULL,
`b` INT(11) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE INDEX `foo_id_b` (`foo_id`, `b`),
CONSTRAINT `FK_BAR_FOO` FOREIGN KEY (`foo_id`) REFERENCES `FOO` (`id`) ON DELETE CASCADE
)
ENGINE=InnoDB
;
Explicit Key Example: db-fiddle
MySQL ignores the redundant indexes, if the table was created with an explicit index that satisfies the foreign key CONSTRAINT.
DROP TABLE IF EXISTS `BAR`;
DROP TABLE IF EXISTS `FOO`;
CREATE TABLE `FOO` (
`id` INT(11) NOT NULL,
PRIMARY KEY (`id`)
)
ENGINE=InnoDB
;
CREATE TABLE `BAR` (
`id` INT(11) NOT NULL,
`foo_id` INT(11) NOT NULL,
`b` INT(11) NOT NULL,
PRIMARY KEY (`id`),
INDEX `FK_BAR_FOO` (`foo_id`),
CONSTRAINT `FK_BAR_FOO` FOREIGN KEY (`foo_id`) REFERENCES `FOO` (`id`) ON DELETE CASCADE
)
ENGINE=InnoDB
;
ALTER TABLE `BAR`
ADD UNIQUE INDEX `foo_id_b` (`foo_id`, `b`);
SHOW CREATE TABLE `BAR`;
Result
Composite-key index for foo_id, b and index on foo_id are created.
CREATE TABLE `BAR` (
`id` INT(11) NOT NULL,
`foo_id` INT(11) NOT NULL,
`b` INT(11) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE INDEX `foo_id_b` (`foo_id`, `b`),
INDEX `FK_BAR_FOO` (`foo_id`),
CONSTRAINT `FK_BAR_FOO` FOREIGN KEY (`foo_id`) REFERENCES `FOO` (`id`) ON DELETE CASCADE
)
ENGINE=InnoDB
;
Solution
In your scripts, verify the index (does not) exist before attempting to drop/add the index.
IF NOT EXISTS(
SELECT 1 FROM INFORMATION_SCHEMA.STATISTICS
WHERE TABLE_NAME = 'cfgAttributeInstances'
AND INDEX_NAME = 'new_nodeComponentID'
AND INDEX_SCHEMA = 'DbName')
THEN
ALTER TABLE `cfgAttributeInstances`
ADD UNIQUE INDEX `new_nodeComponentID` (`nodeComponentID`,`attributeID`);
END IF;
IF EXISTS (
SELECT 1 FROM INFORMATION_SCHEMA.STATISTICS
WHERE TABLE_NAME = 'cfgAttributeInstances'
AND INDEX_NAME = 'nodeComponentID'
AND INDEX_SCHEMA = 'DbName')
THEN
ALTER TABLE `cfgAttributeInstances`
DROP INDEX `nodeComponentID`;
END IF;
I'm building a table with a two part foreign key that references a two part key in another table. It isn't working, and I can't see why because the data types line up.
Can't create table 'tsugi.video_comments' (errno: 150)
Here's the code I'm trying to run:
CREATE TABLE `video_comments` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`video_id` varchar(11) NOT NULL DEFAULT '',
`link_id` int(11) NOT NULL,
`videoTime` int(11) NOT NULL,
`comment` text NOT NULL,
`parent` int(11) unsigned DEFAULT NULL,
`private` tinyint(1) DEFAULT NULL,
`replies` int(11) unsigned DEFAULT '0',
`reports` int(11) DEFAULT '0',
`user_id` int(11) NOT NULL,
`displayname` varchar(2048) DEFAULT NULL,
PRIMARY KEY (`id`),
KEY `video_ibfk_1` (`link_id`),
KEY `video_ibfk_2` (`user_id`),
CONSTRAINT `video_comments_ibfk_1` FOREIGN KEY (`parent`) REFERENCES `video_comments` (`id`) ON DELETE CASCADE,
CONSTRAINT `video_ibfk_1` FOREIGN KEY (`link_id`) REFERENCES `lti_link` (`link_id`) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT `video_ibfk_2` FOREIGN KEY (`user_id`) REFERENCES `lti_user` (`user_id`) ON DELETE CASCADE ON UPDATE CASCADE,
CONSTRAINT `video_key` FOREIGN KEY (`link_id`, `video_id`) REFERENCES `video_ids` (`link_id`, `video_id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=285 DEFAULT CHARSET=utf8;
The command runs successfully if I delete the last constraint, so that's where the problem is, not in the other constraints.
Here's the table it's referencing:
CREATE TABLE `video_ids` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`video_id` varchar(11) NOT NULL DEFAULT '',
`link_id` int(11) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `video_key` (`video_id`,`id`),
KEY `link_id` (`link_id`),
KEY `id` (`id`,`video_id`),
CONSTRAINT `video_ids_ibfk_1` FOREIGN KEY (`link_id`) REFERENCES `t_lti_link` (`link_id`) ON DELETE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
To make sure that the video_id and link_id fields are exactly the same, I copied them directly from the existing table's code to the code for creating the new table. I expected that to solve it, but it did not. Here's the error log:
------------------------
LATEST FOREIGN KEY ERROR
------------------------
141114 22:04:09 Error in foreign key constraint of table tsugi/video_comments:
FOREIGN KEY (`link_id`, `video_id`) REFERENCES `video_ids` (`link_id`, `video_id`) ON DELETE CASCADE ON UPDATE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=285 DEFAULT CHARSET=utf8:
Cannot find an index in the referenced table where the
referenced columns appear as the first columns, or column types
in the table and the referenced table do not match for constraint.
Note that the internal storage type of ENUM and SET changed in
tables created with >= InnoDB-4.1.12, and such columns in old tables
cannot be referenced by such columns in new tables.
See http://dev.mysql.com/doc/refman/5.5/en/innodb-foreign-key-constraints.html
for correct foreign key definition.
Foreign key references need to be to unique or primary keys. So, you can fix this just by having a unique declaration in video_ids:
CREATE TABLE `video_ids` (
`id` int(11) unsigned NOT NULL AUTO_INCREMENT,
`video_id` varchar(11) NOT NULL DEFAULT '',
`link_id` int(11) NOT NULL,
PRIMARY KEY (`id`),
UNIQUE KEY `video_key` (`video_id`,`id`),
KEY `link_id` (`link_id`),
KEY `id` (`id`,`video_id`),
UNIQUE (link_id, video_id),
CONSTRAINT `video_ids_ibfk_1` FOREIGN KEY (`link_id`) REFERENCES `t_lti_link` (`link_id`) ON DELETE CASCADE
) ENGINE=InnoDB AUTO_INCREMENT=2 DEFAULT CHARSET=utf8;
Here is a SQL Fiddle with an example.
I'm new to SQL and trying to learn how to reference on table to another. This is what I have:
CREATE TABLE IF NOT EXISTS itemData (
id int(11) AUTO_INCREMENT PRIMARY KEY,
title varchar(64) NOT NULL,
sector_id int(11) DEFAULT NULL,
status_id int(11) DEFAULT NULL,
locations_id int(11) DEFAULT NULL,
payments_id int(11) DEFAULT NULL,
type_id int(11) DEFAULT NULL,
CONSTRAINT `fk_sector_id` FOREIGN KEY (sector_id) REFERENCES `sector` (`sector_id`),
CONSTRAINT `fk_status_id` FOREIGN KEY (`status_id`) REFERENCES `status` (`status_id`),
CONSTRAINT `fk_locations_id` FOREIGN KEY (`locations_id`) REFERENCES `location` (`locations_id`),
CONSTRAINT `fk_payments_id` FOREIGN KEY (`payments_id`) REFERENCES `payments` (`payments_id`),
CONSTRAINT `fk_type_id` FOREIGN KEY (`type_id`) REFERENCES `type` (`type_id`)
);
Then I have my reference table for example:
CREATE TABLE IF NOT EXISTS itemStatus (
id int(11) AUTO_INCREMENT PRIMARY KEY,
name varchar(64) NOT NULL UNIQUE KEY
);
This doesn't seem to validate, can someone tell me where I have gone wrong please?
You probably need to change your table definition like this:
CREATE TABLE IF NOT EXISTS itemStatus (
status_id int(11) AUTO_INCREMENT PRIMARY KEY,
name varchar(64) NOT NULL UNIQUE KEY
);
as the constraint definition in your table is like this:
CONSTRAINT `fk_status_id` FOREIGN KEY (`status_id`) REFERENCES `itemstatus` (`status_id`),
You need to update the correct table in the constraint.
Also if you dont want to change the table definition then change the constraint like this:
CONSTRAINT `fk_id` FOREIGN KEY (`id`) REFERENCES `itemstatus` (`id`)
Here's your constraint:
CONSTRAINT `fk_status_id` FOREIGN KEY (`status_id`) REFERENCES `status` (`status_id`)
Here's the table definition:
CREATE TABLE IF NOT EXISTS itemStatus (
id int(11) AUTO_INCREMENT PRIMARY KEY,
name varchar(64) NOT NULL UNIQUE KEY
);
There's no column named status_id in that table.
Either rename the primary key column to status_id or change the constraint to point to id.
CREATE TABLE IF NOT EXISTS `questions` (
`question_id` int(11) NOT NULL AUTO_INCREMENT,
`createddate` timestamp NOT NULL DEFAULT CURRENT_TIMESTAMP,
`updateddate` timestamp NULL DEFAULT NULL,
`active_flag` tinyint(4) NOT NULL DEFAULT '0',
PRIMARY KEY (`question_id`),
UNIQUE KEY `id_UNIQUE` (`question_id`)
) ENGINE=InnoDB DEFAULT CHARSET=utf8 AUTO_INCREMENT=1 ;
CREATE TABLE `alarts` (
`alart_id` BIGINT(20) unsigned NOT NULL AUTO_INCREMENT,
`alart_name` varchar(45) NOT NULL,
`interval` int(10) unsigned NOT NULL,
`alart_sent_counter` int(10) unsigned NOT NULL,
`alart_types_id` BIGINT(20) unsigned NOT NULL,
`contact_group_id` int(10) unsigned NOT NULL,
PRIMARY KEY (`alart_id`),
FOREIGN KEY (`alart_types_id`) REFERENCES alart_types(`alart_types_id`)
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;
I want to create new table with two FOREIGN KEY like this:
CREATE TABLE `alart_question_mapping` (
`alart_question_mapping_id` BIGINT(20) unsigned NOT NULL AUTO_INCREMENT,
`question_id` int(11) NOT NULL,
`alart_id` BIGINT(20) unsigned NOT NULL,
PRIMARY KEY (`alart_question_mapping_id`),
FOREIGN KEY (`question_id`) REFERENCES questions(`question_id`),
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;
but I am getting error:
Error Code: 1005. Can't create table 'alart_question_mapping' (errno: 150)
How can I create this table ?
Thank's.
Chane the statement:
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
to
FOREIGN KEY (`alart_id`) REFERENCES alarts(`alart_id`)
The only thing I can see is you are referencing a table in your CREATE TABLE statement that is not present in what you provided:
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
If you remove this reference the table will create. See SQL Fiddle with Demo
Edit #1, based on your update the problem is you are referencing the wrong field in your last table:
Change this:
CREATE TABLE `alart_question_mapping` (
`alart_question_mapping_id` BIGINT(20) unsigned NOT NULL AUTO_INCREMENT,
`question_id` int(11) NOT NULL,
`alart_id` BIGINT(20) unsigned NOT NULL,
PRIMARY KEY (`alart_question_mapping_id`),
FOREIGN KEY (`question_id`) REFERENCES questions(`question_id`),
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
)
To this:
CREATE TABLE `alart_question_mapping` (
`alart_question_mapping_id` BIGINT(20) unsigned NOT NULL AUTO_INCREMENT,
`question_id` int(11) NOT NULL,
`alart_id` BIGINT(20) unsigned NOT NULL,
PRIMARY KEY (`alart_question_mapping_id`),
FOREIGN KEY (`question_id`) REFERENCES questions(`question_id`),
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_types_id`)
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;
So you are changing this line:
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
to this:
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_types_id`)
If you are referencing the alart_types table then you will want to reference the alart_types_id not the alart_id
see SQL Fiddle with Demo
It can't find table alart_types.
From MySQL Foreign Key Constraints
If you re-create a table that was dropped, it must have a definition
that conforms to the foreign key constraints referencing it. It must
have the right column names and types, and it must have indexes on the
referenced keys, as stated earlier. If these are not satisfied, MySQL
returns error number 1005 and refers to error 150 in the error
message.
I think you mean
FOREIGN KEY (`alart_id`) REFERENCES alart(`alart_id`)
instead of
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
Hope this makes sense.
In this table
CREATE TABLE alart_types (
alart_types_id BIGINT(20) unsigned NOT NULL AUTO_INCREMENT,
alarts_types_name varchar(45) NOT NULL,
PRIMARY KEY (alart_types_id)
) ENGINE=InnoDB AUTO_INCREMENT=20 DEFAULT CHARSET=utf8;
it doesn't really make sense to have an autoincrement id number without also having a unique constraint on alarts_types_name. Without that unique constraint, you're almost certain to end up with a table whose data looks like this.
1 Warning
2 Critical
3 Warning
4 Warning
This constraint references a column that doesn't exist.
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_id`)
It should be
FOREIGN KEY (`alart_id`) REFERENCES alart_types(`alart_types_id`)