I searched for a solution to this problem on the Internet and checked the Stack Overflow questions, but none of the solutions worked for my case.
I want to create a foreign key from table sira_no to metal_kod.
ALTER TABLE sira_no
ADD CONSTRAINT METAL_KODU FOREIGN KEY(METAL_KODU)
REFERENCES metal_kod(METAL_KODU)
ON DELETE SET NULL
ON UPDATE SET NULL ;
This script returns:
Error Code: 1005. Can't create table 'ebs.#sql-f48_1a3' (errno: 150)
I tried adding an index to the referenced table:
CREATE INDEX METAL_KODU_INDEX ON metal_kod (METAL_KODU);
I checked METAL_KODU on both tables (charset and collation), but I couldn’t find a solution to this problem. How can I fix this problem?
Here is the metal_kod table:
METAL_KODU varchar(4) NO PRI
DURUM bit(1) NO
METAL_ISMI varchar(30) NO
AYAR_YOGUNLUK smallint(6) YES 100
asked Jan 26, 2012 at 13:14
1
Error Code: 1005 — there is a wrong primary key reference in your code
Usually it’s due to a referenced foreign key field that does not exist. It might be you have a typo mistake, or check case it should be same, or there’s a field-type mismatch. Foreign key-linked fields must match definitions exactly.
Some known causes may be:
- The two key fields type and/or size doesn’t match exactly. For example, if one is
INT(10)the key field needs to beINTas well and notBIGINTorSMALLINTorTINYINT. You should also check that one is notSIGNEDand the other isUNSIGNED. They both need to be exactly the same. - One of the key field that you are trying to reference does not have an index and/or is not a primary key. If one of the fields in the relationship is not a primary key, you must create an index for that field.
- The foreign key name is a duplicate of an already existing key. Check that the name of your foreign key is unique within your database. Just add a few random characters to the end of your key name to test for this.
- One or both of your tables is a
MyISAMtable. In order to use foreign keys, the tables must both beInnoDB. (Actually, if both tables areMyISAMthen you won’t get an error message — it just won’t create the key.) In Query Browser, you can specify the table type. - You have specified a cascade
ONDELETESETNULL, but the relevant key field is set toNOTNULL. You can fix this by either changing your cascade or setting the field to allowNULLvalues. - Make sure that the Charset and Collate options are the same both at the table level as well as individual field level for the key columns.
- You have a default value (that is, default=0) on your foreign key column
- One of the fields in the relationship is part of a combination (composite) key and does not have its own individual index. Even though the field has an index as part of the composite key, you must create a separate index for only that key field in order to use it in a constraint.
- You have a syntax error in your
ALTERstatement or you have mistyped one of the field names in the relationship - The name of your foreign key exceeds the maximum length of 64 characters.
For more details, refer to: MySQL Error Number 1005 Can’t create table
Bill Karwin
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answered Jan 26, 2012 at 13:26
13
This could also happen when exporting your database from one server to another and the tables are listed in alphabetical order by default.
So, your first table could have a foreign key of another table that is yet to be created. In such cases, disable foreign_key_checks and create the database.
Just add the following to your script:
SET FOREIGN_KEY_CHECKS=0;
and it shall work.
answered May 7, 2015 at 13:27
happyhardikhappyhardik
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0
Very often it happens when the foreign key and the reference key don’t have the same type or same length.
answered Aug 25, 2014 at 12:29
zahid9izahid9i
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0
Sometimes it is due to the master table is dropped (maybe by disabling foreign_key_checks), but the foreign key CONSTRAINT still exists in other tables. In my case I had dropped the table and tried to recreate it, but it was throwing the same error for me.
So try dropping all the foreign key CONSTRAINTs from all the tables if there are any and then update or create the table.
answered Feb 1, 2015 at 11:21
rajugrajug
675 bronze badges
I had a similar error. The problem had to do with the child and parent table not having the same charset and collation. This can be fixed by appending ENGINE = InnoDB DEFAULT CHARACTER SET = utf8;
CREATE TABLE IF NOT EXISTS `country` (`id` INT(11) NOT NULL AUTO_INCREMENT,...) ENGINE = InnoDB DEFAULT CHARACTER SET = utf8;
… on the SQL statement means that there is some missing code.
answered Jul 14, 2016 at 8:34
davidbwiredavidbwire
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The foreign key has to have the exact same type as the primary key that it references. For the example has the type “INT UNSIGNED NOT NULL” the foreing key also have to “INT UNSIGNED NOT NULL”
CREATE TABLE employees(
id_empl INT UNSIGNED NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id)
);
CREATE TABLE offices(
id_office INT UNSIGNED NOT NULL AUTO_INCREMENT,
id_empl INT UNSIGNED NOT NULL,
PRIMARY KEY(id),
CONSTRAINT `constraint1` FOREIGN KEY (`id_empl`) REFERENCES `employees` (`id_empl`) ON DELETE CASCADE ON UPDATE CASCADE ) ENGINE=InnoDB DEFAULT CHARSET=utf8 COMMENT='my offices';
answered Feb 15, 2017 at 13:10
1
Error Code: 1005
I had a similar issue, so here are few things that I did try (not in any order, except for the solution 
)
- Changed the foreign key names (it didn’t work)
- Reduced the foreign key length
- Verified the datatypes (darn nothing wrong)
- Check indexes
- Check the collations (everything fine, darn again)
- Truncated the table, of no good use
- Dropped the table and re-created
- Tried to see if any circular reference is being created — all fine
-
Finally, I saw that I had two editors open. One that in PhpStorm (JetBrains) and the other MySQL workbench. It seems that the PhpStorm / MySQL Workbench creates some kind of edit lock.
I closed PhpStorm just to check if locking was the case (it could have been the other way around). This solved my problem.
answered May 7, 2016 at 3:18
I had the very same error message. Finally I figured out I misspelled the name of the table in the command:
ALTER TABLE `users` ADD FOREIGN KEY (country_id) REFERENCES country (id);
versus
ALTER TABLE `users` ADD FOREIGN KEY (country_id) REFERENCES countries (id);
I wonder why on earth MySQL cannot tell such a table does not exist…
answered Feb 7, 2017 at 3:04
MyISAM has been just mentioned. Simply try adding ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ; at the end of a statement, assuming that your other tables were created with MyISAM.
CREATE TABLE IF NOT EXISTS `tablename` (
`key` bigint(20) NOT NULL AUTO_INCREMENT,
FOREIGN KEY `key` (`key`) REFERENCES `othertable`(`id`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1 AUTO_INCREMENT=2 ;
answered Jan 20, 2016 at 23:29
3xCh1_233xCh1_23
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In my case, it happened when one table is InnoB and other is MyISAM. Changing engine of one table, through MySQL Workbench, solves for me.
answered Mar 28, 2016 at 2:01
rkawanorkawano
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It happened in my case, because the name of the table being referenced in the constraint declaration wasn’t correct (I forgot the upper case in the table name):
ALTER TABLE `Window` ADD CONSTRAINT `Windows_ibfk_1` FOREIGN KEY (`WallId`) REFERENCES `Wall` (`id`) ON DELETE CASCADE ON UPDATE CASCADE;
answered Mar 10, 2015 at 15:45
check both tables has same schema InnoDB MyISAM. I made them all the same in my case InnoDB and worked
answered Sep 21, 2019 at 2:35
Brian SanchezBrian Sanchez
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My problem was not listed, it was something so silly …..
The table that has the FK as PK was a composite PK that was declared like this: primary key (CNPJ, CEP)
I wanted the CEP field to be FK in another table and I was stuck in this error, the moral of the story just inverted the code above for Primary key (CEP, CNPJ) and it worked.
Get tip their friends.
answered Jun 8, 2020 at 4:49
Дата: 2.12.2016
Автор: Василий Лукьянчиков , vl (at) sqlinfo (dot) ru
Функционирование внешних ключей в MySQL имеет много нюансов и ограничений из-за чего существует немало возможностей получить ошибку при работе с ними. Одна из проблем состоит в том, что сообщения об ошибках содержат мало полезной информации и не указывают причину возникновения ошибки. В данной статье дается объяснение как получить дополнительную информацию об ошибке и приведен полный список причин возникновения ошибок внешних ключей. Каждая причина снабжена уникальным буквенно-цифровым кодом (А4, Б1, ..), использующимся в сводной таблице в конце статьи, которая поможет вам быстро диагностировать проблему.
Внешний ключ — это поле (или набор полей) в таблице, называемой дочерней, которое ссылается на поле (или набор полей) в таблице, называемой родительской. Дочерняя и родительская таблицы могут совпадать, т.е. таблица будет ссылаться на саму себя. Внешние ключи позволяют связать записи в двух таблицах по определенным полям так, что при обновлении поля в родительской автоматически происходит изменение записи в дочерней таблице.
В MySQL внешние ключи не реализованы на уровне сервера, их поддержка зависит от используемого хранилища данных. Содержание статьи справедливо для InnoDB (в том числе и для XtraDB).
Как получить больше данных об ошибке
После получения ошибки выполните SHOW ENGINE INNODB STATUS и смотрите содержимое секции LATEST FOREIGN KEY ERROR. Этот способ имеет следующие недостатки:
- требует привилегии SUPER
- содержит информацию о последней ошибке, связанной с внешними ключами, из-за чего нужно выполнять SHOW ENGINE INNODB STATUS сразу после возникновения ошибки, что не всегда удобно/возможно
- используются внутренние имена таблиц (например, ‘test.#sql-d88_b’), что затрудняет диагностику
- порой содержит мало полезной информации или таковая вообще отсутствует.
Альтернатива: использовать MariaDB версий больше 5.5.45 и 10.0.21, в которых сообщения об ошибках значительно улучшены и указывают причину возникновения ошибки.
Errno 150
Если в сообщении об ошибке содержится errno 150 (или errno 121), значит парсер MySQL не смог распознать ошибку и передал команду (create/alter) на выполнение в InnoDB. В этом разделе перечислены ситуации, приводящие к ошибкам, содержащим errno 150.
А1. Нет индекса в родительской таблице. Набор полей, на которые ссылается дочерняя таблица, должен быть проиндексирован (или являться левой частью другого индекса). Порядок полей в индексе должен быть таким же как в определении внешнего ключа. Сюда же относится случай отсутствия нужной колонки в родительской таблице (нет колонки, нет и индекса).
Неочевидный момент: на колонке родительской таблицы есть индекс — полнотекстовый (fulltext). Но внешний ключ всё равно не создается и сервер ругается на отсутствие индекса. Это происходит потому, что индекс должен быть обычным (btree).
Другой неочевидный момент: на колонке родительской таблицы есть индекс — префиксный. Но внешний ключ всё равно не создается и сервер ругается на отсутствие индекса. Это происходит потому, что индекс должен быть определен на всей длине колонки.
Строго говоря, поля в дочерней таблице тоже должны быть проиндексированы, но если нет подходящего индекса, MySQL автоматически его создаст при добавлении внешнего ключа (в совсем уж древних версиях требовалось предварительное создание индекса).
Примеры
create table t1 (a int, b int, index(a)) engine=innodb;
create table t2 (a int, foreign key (a) references t1(a), foreign key (a) references t1(b)) engine=innodb;
ERROR 1005 (HY000): Cannot create table ‘test.t2’ (errno: 150)
SHOW ENGINE INNODB STATUS;
————————
LATEST FOREIGN KEY ERROR
————————
2016-11-16 06:37:39 0x14c1c Error in foreign key constraint of table test/t2:
foreign key (a) references t1(b)) engine=innodb:
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.
Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-foreign-key-constr
aints.html for correct foreign key definition.
————
— при использовании оператора ALTER ошибка и секция
— LATEST FOREIGN KEY ERROR будут содержать внутреннее имя таблицы test.#sql-a64_1
create table t2 (a int) engine=innodb;
alter table t2 add foreign key (a) references t1(a), add foreign key (a) references t1(b);
ERROR 1005 (HY000): Cannot create table ‘test.#sql-a64_1’ (errno: 150)
— в новых версиях парсер MySQL определяет некорректность
— конструкции и возвращает другую ошибку (без errno 150)
alter table t2 add foreign key (a) references t1(a), add foreign key (a) references t1(b);
ERROR 1215 (HY000): Cannot add foreign key constraint
— аналогично и для оператора CREATE
drop table t2;
create table t2 (a int, foreign key (a) references t1(a), foreign key (a) references t1(b)) engine=innodb;
ERROR 1215 (HY000): Cannot add foreign key constraint
Обратите внимание, если внешний ключ уже существует и в результате изменений (alter table) возникает ситуация отсутствия индекса в родительской таблице, то код ошибки будет 1025:
create table t1 (a int, b int, index(a)) engine=innodb;
create table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
alter table t1 drop a;
ERROR 1025 (HY000): Error on rename of ‘.test#sql-d6c_5′ to ‘.testt1′ (errno: 150)
show engine innodb status;
————————
LATEST FOREIGN KEY ERROR
————————
161220 7:14:25 Error in foreign key constraint of table test/t2:
there is no index in referenced table which would contain
the columns as the first columns, or the data types in the
referenced table do not match the ones in table. Constraint:
,
CONSTRAINT «t2_ibfk_1» FOREIGN KEY («a») REFERENCES «t1» («a»)
The index in the foreign key in table is «a»
See http://dev.mysql.com/doc/refman/5.5/en/innodb-foreign-key-constraints.html
for correct foreign key definition.
InnoDB: Renaming table `test`.`#sql-d6c_5` to `test`.`t1` failed!
———
А2. Родительская таблица не найдена в словаре данных InnoDB. Это означает, что родительская таблица должна существовать и быть постоянной InnoDB таблицей. Не временной InnoDB таблицей, так как информация о временных таблицах не сохраняется в словаре данных InnoDB. И уж тем более не представлением.
Примеры
mysql> create table t1 (a int, index(a)) engine=myisam;
mysql> create table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
ERROR 1215 (HY000): Cannot add foreign key constraint
— в старых версиях будет ошибка вида
ERROR 1005 (HY000): Cannott create table ‘test.t2’ (errno: 150)
show engine innodb status;
————————
LATEST FOREIGN KEY ERROR
————————
2016-11-17 16:30:09 0x364c Error in foreign key constraint of table world/t2:
foreign key (a) references t1(a)) engine=innodb:
Cannot resolve table name close to:
(a)) engine=innodb
————
А3. Синтаксическая ошибка. Внешние ключи реализованы на уровне хранилища, и в старых версиях парсер сервера MySQL не распознавал синтаксические ошибки внешних ключей, из-за чего их было трудно идентифицировать.
Примеры
Например, в определении внешнего ключа количество столбцов дочерней таблицы не совпадает с количеством столбцов родительской таблицы:
create table t1(id int not null primary key, b int, key(b)) engine=innodb;
Query OK, 0 rows affected (0.22 sec)
alter table t1 add foreign key(id,b) references t1(id);
ERROR 1005 (HY000): Can‘t create table ‘test.#sql-d88_b’ (errno: 150)
show warnings;
+——-+——+—————————————————+
| Level | Code | Message |
+——-+——+—————————————————+
| Error | 1005 | Can‘t create table ‘test.#sql-d88_b’ (errno: 150) |
+——-+——+—————————————————+
— понять, что причина в синтаксической ошибке
— можно только из:
show engine innodb status;
————————
LATEST FOREIGN KEY ERROR
————————
160605 22:28:23 Error in foreign key constraint of table test/#sql-d88_b:
foreign key(id,b) references t1(id):
Syntax error close to:
— в новых версиях парсер распознает синтаксическую ошибку
— и сообщает об этом:
ERROR 1239 (42000): Incorrect foreign key definition for ‘foreign key without name’: Key reference and table reference don‘t match
Другой пример: попробуем создать внешний ключ на поле типа text:
create table t1 (a text , index(a(50))) engine=innodb;
create table t2 (a text, foreign key (a) references t1(a)) engine=innodb;
ERROR 1170 (42000): BLOB/TEXT column ‘a’ used in key specification without a key length
— MySQL автоматически пытается создать индекс на колонке `a`, и
— сообщает, что нельзя создать индекс по всей длине поля типа text.
— Хорошо, укажем префикс и получим errno 150:
create table t2 (a text, foreign key (a(50)) references t1(a)) engine=innodb;
ERROR 1005 (HY000): Cannot create table ‘test.t2’ (errno: 150)
— понять, что произошла ошибка синтаксиса можно:
— или через show engine innodb status;
— или внимательно сравнить разрешенный синтаксис в документации
— с написанной командой.
А4. Несовпадение типов данных. Столбцы дочерней таблицы, входящие в определение внешнего ключа, должны иметь такие же типы данных, что и столбцы родительской таблицы, на которые они ссылаются, вплоть до атрибутов: знак и кодировка/сопоставление.
Примеры
— например, если у одной колонки мы определим
— атрибут unsigned, а у другой нет, то:
create table t1 (a int unsigned, index(a)) engine=innodb;
create table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
ERROR 1215 (HY000): Cannot add foreign key constraint
— в старых версиях будет ошибка вида
ERROR 1005 (HY000): Cannott create table ‘test.t2’ (errno: 150)
show engine innodb status;
————————
LATEST FOREIGN KEY ERROR
————————
2016-11-26 03:00:47 0x10894 Error in foreign key constraint of table world/t2:
foreign key (a) references t1(a)) engine=innodb:
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.
Please refer to http://dev.mysql.com/doc/refman/5.7/en/innodb-foreign-key-constr
aints.html for correct foreign key definition.
————
Если несоответствие типов данных возникает во время изменения таблицы при уже существующем внешнем ключе, то ошибка будет иметь вид:
create table t1 (a int, index(a)) engine=innodb;
create table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
MariaDB [test]> alter table t1 modify a int unsigned;
ERROR 1025 (HY000): Error on rename of ‘.test#sql-d6c_6′ to ‘.testt1′ (errno: 150)
А5. Некорректно задано действие внешнего ключа. Если в определении внешнего ключа указано ON UPDATE SET NULL и/или ON DELETE SET NULL, то соответствующие столбцы дочерней таблицы не должны быть определены как NOT NULL.
Примеры
create table t1 (a int not null, index(a)) engine=innodb;
create table t2 (a int not null, foreign key (a) references t1(a) on delete set null) engine=innodb;
ERROR 1215 (HY000): Cannot add foreign key constraint
— в старых версиях будет:
ERROR 1005 (HY000): Cannot create table ‘test.t2’ (errno: 150)
show engine innodb status;
————————
LATEST FOREIGN KEY ERROR
————————
2016-11-26 06:24:42 0x10894 Error in foreign key constraint of table world/t2:
foreign key (a) references t1(a) on delete set null) engine=innodb:
You have defined a SET NULL condition though some of the
columns are defined as NOT NULL.
————
Если коллизия возникает при уже существующем внешнем ключе, то:
create table t1 (a int not null, index(a)) engine=innodb;
create table t2 (a int, foreign key (a) references t1(a) on delete set null) engine=innodb;
alter table t2 modify a int not null;
ERROR 1025 (HY000): Error on rename of ‘.test#sql-d6c_6′ to ‘.testt2′ (errno: 150)
А6. Дочерняя таблица является временной InnoDB таблицей. Внешние ключи можно создавать только в постоянной, несекционированной InnoDB таблице.
Примеры
create table t1 (a int, index(a)) engine=innodb;
create temporary table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
ERROR 1005 (HY000): Cannot create table ‘test.t2’ (errno: 150)
show engine innodb status;
————————
LATEST FOREIGN KEY ERROR
————————
161130 4:22:26 Error in foreign key constraint of table temp/#sql318_4_1:
foreign key (a) references t1(a)) engine=innodb:
Cannot resolve table name close to:
(a)) engine=innodb
———
— в новых версиях ошибка будет иметь вид:
ERROR 1215 (HY000): Cannot add foreign key constraint
А7. Родительская таблица является секционированной таблицей. На данный момент (MySQL 5.7 и MariaDB 10.1) внешние ключи не поддерживаются для секционированных таблиц (partitioned tables). Иными словами, ни родительская, ни дочерняя таблица не должны иметь секции. В случае, когда внешний ключ ссылается на секционированную таблицу диагностика ошибки затруднена ошибкой вывода show engine innodb status:
Примеры
create table t1 (a int, index(a)) partition by range (a)
(partition p0 values less than (10),
partition p1 values less than (20),
partition p2 values less than maxvalue);
create table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
ERROR 1005 (HY000): Cannot create table ‘test.t2’ (errno: 150)
show engine innodb status;
————————
LATEST FOREIGN KEY ERROR
————————
161223 19:38:14 Error in foreign key constraint of table test/t2:
foreign key (a) references t1(a)) engine=innodb:
Cannot resolve table name close to:
(a)) engine=innodb
———
— сообщение указывает на то, что родительская таблица
— не найдена в словаре данных innodb (bug: 84331)
— в новых версиях ошибка будет иметь вид:
create table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
ERROR 1215 (HY000): Cannot add foreign key constraint
Если разбивать на секции родительскую таблицу после создания внешнего ключа, то
create table t1 (a int, index(a)) engine=innodb;
create table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
alter table t1 PARTITION BY HASH(a) PARTITIONS 8;
ERROR 1217 (23000): Cannot delete or update a parent row: a foreign key constraint fails
show engine innodb status;
— не содержит секцию LATEST FOREIGN KEY ERROR
Errno 121
Такой результат возникает только в одном случае.
Б1. Неуникальное имя ограничения. Обратите внимание: речь не о имени внешнего ключа. Если при создании внешнего ключа вы указываете не обязательное ключевое слово CONSTRAINT, то идущий после него идентификатор должен быть уникальным в пределах базы данных.
Примеры
create table t1 (a int, index(a)) engine=innodb;
create table t2 (a int, CONSTRAINT q1 foreign key (a) references t1(a)) engine=innodb;
create table t3 (a int, CONSTRAINT q1 foreign key (a) references t1(a)) engine=innodb;
ERROR 1005 (HY000): Cannot create table ‘test.t3’ (errno: 121)
— в 5.7 будет другая ошибка
ERROR 1022 (23000): Cannot write; duplicate key in table ‘t3’
show engine innodb status;
————————
LATEST FOREIGN KEY ERROR
————————
161130 3:31:11 Error in foreign key constraint creation for table `test`.`t3`.
A foreign key constraint of name `test`.`q1`
already exists. (Note that internally InnoDB adds ‘databasename’
in front of the user-defined constraint name.)
Note that InnoDB FOREIGN KEY system tables store
constraint names as case-insensitive, with the
MySQL standard latin1_swedish_ci collation. If you
create tables or databases whose names differ only in
the character case, then collisions in constraint
names can occur. Workaround: name your constraints
explicitly with unique names.
———
Нет ошибок
Внешний ключ не создается, и нет никаких ошибок. Это может происходить по следующим причинам:
В1. Дочерняя таблица не является InnoDB таблицей. В этом случае для совместимости с другими субд парсер MySQL просто проигнорирует конструкцию внешнего ключа.
Примеры
create table t1 (a int, index(a)) engine=innodb;
create table t2 (a int, foreign key (a) references t1(a)) engine=myisam;
Query OK, 0 rows affected (0.33 sec)
MariaDB [test]> show create table t2G
*************************** 1. row ***************************
Table: t2
Create Table: CREATE TABLE `t2` (
`a` int(11) DEFAULT NULL,
KEY `a` (`a`)
) ENGINE=MyISAM DEFAULT CHARSET=latin1
1 row in set (0.00 sec)
В2. Не соответствует синтаксису MySQL. Стандарт SQL разрешает указывать внешний ключ сразу при объявлении колонки с помощью конструкции REFERENCES (например, … a int references t1(a), …), однако MySQL игнорирует такую форму записи. Единственный способ создать в нем внешний ключ — это использовать отдельный блок FOREIGN KEY:
[CONSTRAINT [symbol]] FOREIGN KEY
[index_name] (index_col_name, …)
REFERENCES tbl_name (index_col_name,…)
[ON DELETE reference_option]
[ON UPDATE reference_option]
reference_option:
RESTRICT | CASCADE | SET NULL | NO ACTION | SET DEFAULT
Несоответствие данных
В этой части собраны ошибки, которые возникают из-за нарушения ссылочной целостности, т.е. наличие в дочерней таблице записей, которым нет соответствия в родительской таблице.
Г1. Удаление родительской таблицы. Нельзя удалить родительскую таблицу при наличии внешнего ключа.
create table t1 (a int, index(a)) engine=innodb;
create table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
drop table t1;
ERROR 1217 (23000): Cannot delete or update a parent row: a foreign key constraint fails
Удаление следует понимать в расширенном варианте как удаление из множества InnoDB таблиц. Например, если мы сменим (alter table) движок родительской таблицы на MyISAM, то с точки зрения ограничения внешнего ключа родительская таблица перестанет существовать (т.к. она должна быть постоянной innodb таблицей):
alter table t1 engine=myisam;
ERROR 1217 (23000): Cannot delete or update a parent row: a foreign key constraint fails
Сначала нужно удалить внешний ключ (или всю дочернюю таблицу, что удалит в том числе и внешний ключ). Если вы не знаете какие таблицы являются дочерними для заданной таблицы, то это можно определить через запрос к information_schema:
select table_name from information_schema.key_column_usage
where table_schema = «test» and references_table_name = «t1»;
Г2. Изменение данных в родительской таблице. Если в определении внешнего ключа не задано действие при update/delete, то такие операции над родительской таблицей могут привести к несогласованности данных, т.е. появлению в дочерней таблице записей не имеющих соответствия в родительской таблице.
Примеры
create table t1 (a int, index(a)) engine=innodb;
create table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
insert into t1 values(1);
insert into t2 values(1);
update t1 set a=2;
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1`(`a`))
Г3. Изменение данных в дочерней таблице. Если insert/update записи в дочерней таблицы приводит к несогласованности данных, то
Примеры
create table t1 (a int, index(a)) engine=innodb;
create table t2 (a int, foreign key (a) references t1(a)) engine=innodb;
insert into t2 values(15);
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1` (`a`))
Г4. Добавление внешнего ключа на не пустую таблицу. При попытке добавить внешний ключ на таблицу, в которой есть записи, не удовлетворяющие условию внешнего ключа (т.е. не имеющие соответствия в родительской таблице), будет ошибка:
Примеры
create table t1 (a int, index(a)) engine=innodb;
create table t2 (a int, index(a)) engine=innodb;
insert into t2 values(2);
alter table t2 add foreign key (a) references t1(a);
ERROR 1452 (23000): Cannot add or update a child row: a foreign key constraint fails (`test`.`#sql-3f0_4`, CONSTRAINT `#sql-3f0_4_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1` (`a`))
Г5. Не уникальный ключ в родительской таблице. По стандарту SQL набор полей, на которые ссылается внешний ключ, должен быть уникальным. Однако, реализация внешних ключей в InnoDB позволяет иметь несколько «родителей». Из-за этого возникает трудно диагностируемая ошибка:
Примеры
create table t1 (a int, index(a)) engine=innodb;
create table t2 (a int, index(a)) engine=innodb;
insert into t1 values (1),(1);
insert into t2 values(1);
delete from t1 where a=1 limit 1;
ERROR 1451 (23000): Cannot delete or update a parent row: a foreign key constraint fails (`test`.`t2`, CONSTRAINT `t2_ibfk_1` FOREIGN KEY (`a`) REFERENCES `t1`(`a`))
Сводная таблица
По вертикали расположены коды ошибок MySQL, которые возникают при работе с внешними ключами («нет ошибок» соответствует ситуации, когда сервер не генерирует ошибку, но и не создает внешний ключ). По горизонтали — идентификаторы причин, которые могут привести к ошибке. Плюсы на пересечении указывают какие причины приводят к той или иной ошибке.
| А1 | А2 | А3 | А4 | А5 | А6 | А7 | Б1 | В1 | В2 | Г1 | Г2 | Г3 | Г4 | Г5 | |
| MySQL error 1005 | + | + | + | + | + | + | + | + | |||||||
| MySQL error 1022 | + | ||||||||||||||
| MySQL error 1025 | + | + | + | ||||||||||||
| MySQL error 1215 | + | + | + | + | + | ||||||||||
| MySQL error 1217 | + | + | |||||||||||||
| MySQL error 1239 | + | ||||||||||||||
| MySQL error 1451 | + | + | |||||||||||||
| MySQL error 1452 | + | + | |||||||||||||
| нет ошибок | + | + |
P.S. Если ваш случай не рассмотрен в статье, то задавайте вопрос на форуме SQLinfo. Вам ответят, а статья будет расширена.
Дата публикации: 2.12.2016
© Все права на данную статью принадлежат порталу SQLInfo.ru. Перепечатка в интернет-изданиях разрешается только с указанием автора и прямой ссылки на оригинальную статью. Перепечатка в бумажных изданиях допускается только с разрешения редакции.
Introduction
A foreign key is a field (or collection of fields) in one table that uniquely identifies a row of another table. The table containing the foreign key is called the child table, and the table containing the candidate key is called the referenced or parent table. The purpose of the foreign key is to identify a particular row of the referenced table. Therefore, it is required that the foreign key is equal to the candidate key in some row of the primary table, or else have no value (the NULL value). This is called a referential integrity constraint between the two tables. Because violations of these constraints can be the source of many database problems, most database management systems provide mechanisms to ensure that every non-null foreign key corresponds to a row of the referenced table. Consider following simple example:
create table parent (
id int not null primary key,
name char(80)
) engine=innodb;
create table child (
id int not null,
name char(80),
parent_id int,
foreign key(parent_id) references parent(id)
) engine=innodb;
As far as I know, the following storage engines for MariaDB and/or MySQL support foreign keys:
- InnoDB (both innodb_plugin and XtraDB)
- PBXT (https://mariadb.com/kb/en/mariadb/about-pbxt/)
- SolidDB for MySQL (http://sourceforge.net/projects/soliddb/)
- ScaleDB (https://mariadb.com/kb/en/mariadb/scaledb/ and http://scaledb.com/pdfs/TechnicalOverview.pdf)
- MySQL Cluster NDB 7.3 or later (https://dev.mysql.com/doc/refman/5.6/en/mysql-cluster-ndb-innodb-engines.html)
MariaDB foreign key syntax is documented at https://mariadb.com/kb/en/mariadb/foreign-keys/ (and MySQL at http://dev.mysql.com/doc/refman/5.5/en/innodb-foreign-key-constraints.html). While most of the syntax is parsed and checked when the CREATE TABLE or ALTER TABLE clause is parsed, there are still several error cases that can happen inside InnoDB. Yes, InnoDB has its own internal foreign key constraint parser (in dict0dict.c function dict_create_foreign_constraints_low()).
However, the error messages shown in CREATE or ALTER TABLE, and SHOW WARNINGS in versions of MariaDB prior to 5.5.45 and 10.0.21 are not very informative or clear. There are additional error messages if you issue SHOW ENGINE INNODB STATUS, which help, but were not an ideal solution. In this blog I’ll present a few of the most frequent error cases using MariaDB 5.5.44 and how these error messages are improved in MariaDB 5.5.45 and 10.0.21. I will use the default InnoDB (i.e. XtraDB) but innodb_plugin works very similarly.
Constraint name not unique
Foreign name constraint names must be unique in a database. However, the error message is unclear and leaves a lot unclear:
-------------- CREATE TABLE t1 ( id int(11) NOT NULL PRIMARY KEY, a int(11) NOT NULL, b int(11) NOT NULL, c int not null, CONSTRAINT test FOREIGN KEY (b) REFERENCES t1 (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 -------------- Query OK, 0 rows affected (0.45 sec) -------------- CREATE TABLE t2 ( id int(11) NOT NULL PRIMARY KEY, a int(11) NOT NULL, b int(11) NOT NULL, c int not null, CONSTRAINT mytest FOREIGN KEY (c) REFERENCES t1(id), CONSTRAINT test FOREIGN KEY (b) REFERENCES t2 (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 -------------- ERROR 1005 (HY000): Can't create table `test`.`t2` (errno: 121 "Duplicate key on write or update") -------------- show warnings -------------- +---------+------+--------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+--------------------------------------------------------------------------------+ | Error | 1005 | Can't create table `test`.`t2` (errno: 121 "Duplicate key on write or update") | | Warning | 1022 | Can't write; duplicate key in table 't2' | +---------+------+--------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
These messages are not very helpful because there are two foreign key constraints. Looking into SHOW ENGINE INNODB STATUS we get a better message:
show engine innodb status -------------- ------------------------ LATEST FOREIGN KEY ERROR ------------------------ 2015-07-30 12:37:48 7f44a1111700 Error in foreign key constraint creation for table `test`.`t2`. A foreign key constraint of name `test`.`test` already exists. (Note that internally InnoDB adds 'databasename' in front of the user-defined constraint name.) Note that InnoDB's FOREIGN KEY system tables store constraint names as case-insensitive, with the MySQL standard latin1_swedish_ci collation. If you create tables or databases whose names differ only in the character case, then collisions in constraint names can occur. Workaround: name your constraints explicitly with unique names.
In MariaDB 5.5.45 and 10.0.21, the message is clearly improved:
CREATE TABLE t1 ( id int(11) NOT NULL PRIMARY KEY, a int(11) NOT NULL, b int(11) NOT NULL, c int not null, CONSTRAINT test FOREIGN KEY (b) REFERENCES t1 (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 -------------- Query OK, 0 rows affected (0.14 sec) -------------- CREATE TABLE t2 ( id int(11) NOT NULL PRIMARY KEY, a int(11) NOT NULL, b int(11) NOT NULL, c int not null, CONSTRAINT mytest FOREIGN KEY (c) REFERENCES t1(id), CONSTRAINT test FOREIGN KEY (b) REFERENCES t2 (id) ) ENGINE=InnoDB DEFAULT CHARSET=latin1 -------------- ERROR 1005 (HY000): Can't create table 'test.t2' (errno: 121) -------------- show warnings -------------- +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 121 | Create or Alter table `test`.`t2` with foreign key constraint failed. Foreign key constraint `test/test` already exists on data dictionary. Foreign key constraint names need to be unique in database. Error in foreign key definition: CONSTRAINT `test` FOREIGN KEY (`b`) REFERENCES `test`.`t2` (`id`). | | Error | 1005 | Can't create table 'test.t2' (errno: 121) | +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
No index
There should be an index for columns in a referenced table that contains referenced columns as the first columns.
create table t1(a int, b int, key(b)) engine=innodb -------------- Query OK, 0 rows affected (0.46 sec) -------------- create table t2(a int, b int, constraint b foreign key (b) references t1(b), constraint a foreign key a (a) references t1(a)) engine=innodb -------------- ERROR 1005 (HY000): Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed") -------------- show warnings -------------- +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 150 | Create table 'test/t2' with foreign key constraint failed. There is no index in the referenced table where the referenced columns appear as the first columns. | | Error | 1005 | Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed") | | Warning | 1215 | Cannot add foreign key constraint | +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+ 3 rows in set (0.00 sec)
Fine but again we have no idea which foreign key it was. As before, there is a better message in the SHOW ENGINE INNODB STATUS output:
LATEST FOREIGN KEY ERROR ------------------------ 2015-07-30 13:44:31 7f30e1520700 Error in foreign key constraint of table test/t2: foreign key a (a) references t1(a)) engine=innodb: 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/5.6/en/innodb-foreign-key-constraints.html for correct foreign key definition.
In MariaDB 5.5.45 and 10.0.21, the message is clearly improved:
create table t1(a int, b int, key(b)) engine=innodb -------------- Query OK, 0 rows affected (0.16 sec) -------------- create table t2(a int, b int, constraint b foreign key (b) references t1(b), constraint a foreign key a (a) references t1(a)) engine=innodb -------------- ERROR 1005 (HY000): Can't create table 'test.t2' (errno: 150) -------------- show warnings -------------- +---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 150 | Create table '`test`.`t2`' with foreign key constraint failed. There is no index in the referenced table where the referenced columns appear as the first columns. Error close to foreign key a (a) references t1(a)) engine=innodb. | | Error | 1005 | Can't create table 'test.t2' (errno: 150) | +---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
Referenced table not found
A table that is referenced on foreign key constraint should exist in InnoDB data dictionary. If not:
create table t1 (f1 integer primary key) engine=innodb -------------- Query OK, 0 rows affected (0.47 sec) -------------- alter table t1 add constraint c1 foreign key (f1) references t11(f1) -------------- ERROR 1005 (HY000): Can't create table `test`.`#sql-2612_2` (errno: 150 "Foreign key constraint is incorrectly formed") -------------- show warnings -------------- +---------+------+-----------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-----------------------------------------------------------------------------------------------------+ | Error | 1005 | Can't create table `test`.`#sql-2612_2` (errno: 150 "Foreign key constraint is incorrectly formed") | | Warning | 1215 | Cannot add foreign key constraint | +---------+------+-----------------------------------------------------------------------------------------------------+ show engine innodb status -------------- LATEST FOREIGN KEY ERROR ------------------------ 2015-07-30 13:44:34 7f30e1520700 Error in foreign key constraint of table test/#sql-2612_2: foreign key (f1) references t11(f1): Cannot resolve table name close to: (f1)
Both messages are first referring to an internal table name and the foreign key error message is referring to an incorrect name. In MariaDB 5.5.45 and 10.0.21, the message is clearly improved:
create table t1 (f1 integer primary key) engine=innodb -------------- Query OK, 0 rows affected (0.11 sec) -------------- alter table t1 add constraint c1 foreign key (f1) references t11(f1) -------------- ERROR 1005 (HY000): Can't create table 'test.#sql-2b40_2' (errno: 150) -------------- show warnings -------------- +---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 150 | Alter table `test`.`t1` with foreign key constraint failed. Referenced table `test`.`t11` not found in the data dictionary close to foreign key (f1) references t11(f1). | | Error | 1005 | Can't create table 'test.#sql-2b40_2' (errno: 150) | +---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec) -------------- show engine innodb status -------------- 150730 13:50:36 Error in foreign key constraint of table `test`.`t1`: Alter table `test`.`t1` with foreign key constraint failed. Referenced table `test`.`t11` not found in the data dictionary close to foreign key (f1) references t11(f1).
Temporary tables
Temporary tables can’t have foreign key constraints because temporary tables are not stored to the InnoDB data dictionary.
create temporary table t2(a int, foreign key(a) references t1(a)) engine=innodb -------------- ERROR 1005 (HY000): Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed") -------------- show warnings -------------- +---------+------+--------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+--------------------------------------------------------------------------------------------+ | Error | 1005 | Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed") | | Warning | 1215 | Cannot add foreign key constraint | +---------+------+--------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec) -------------- show engine innodb status -------------- LATEST FOREIGN KEY ERROR ------------------------ 2015-07-30 13:44:35 7f30e1520700 Error in foreign key constraint of table tmp/#sql2612_2_1: foreign key(a) references t1(a)) engine=innodb: Cannot resolve table name close to: (a)) engine=innodb -------------- alter table t1 add foreign key(b) references t1(a) -------------- ERROR 1005 (HY000): Can't create table `test`.`#sql-2612_2` (errno: 150 "Foreign key constraint is incorrectly formed") -------------- show warnings -------------- +---------+------+-----------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-----------------------------------------------------------------------------------------------------+ | Error | 1005 | Can't create table `test`.`#sql-2612_2` (errno: 150 "Foreign key constraint is incorrectly formed") | | Warning | 1215 | Cannot add foreign key constraint | +---------+------+-----------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
These error messages do not really help the user, because the actual reason for the error is not printed and the foreign key error references an internal table name. In MariaDB 5.5.45 and 10.0.21 this is clearly improved:
create temporary table t1(a int not null primary key, b int, key(b)) engine=innodb -------------- Query OK, 0 rows affected (0.04 sec) -------------- create temporary table t2(a int, foreign key(a) references t1(a)) engine=innodb -------------- ERROR 1005 (HY000): Can't create table 'test.t2' (errno: 150) -------------- show warnings -------------- +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 150 | Create table `tmp`.`t2`Ï with foreign key constraint failed. Referenced table `tmp`.`t1` not found in the data dictionary close to foreign key(a) references t1(a)) engine=innodb. | | Error | 1005 | Can't create table 'test.t2' (errno: 150) | +---------+------+-------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec) -------------- alter table t1 add foreign key(b) references t1(a) -------------- ERROR 1005 (HY000): Can't create table 'test.#sql-2b40_2' (errno: 150) -------------- show warnings -------------- +---------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 150 | Alter table `tmp`.`t1`Ï with foreign key constraint failed. Referenced table `tmp`.`t1` not found in the data dictionary close to foreign key(b) references t1(a). | | Error | 1005 | Can't create table 'test.#sql-2b40_2' (errno: 150) | +---------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
Column count does not match
There should be exactly the same number of columns in both the foreign key column list and the referenced column list. However, this currently raises the following error:
create table t1(a int not null primary key, b int, key(b)) engine=innodb -------------- Query OK, 0 rows affected (0.17 sec) -------------- alter table t1 add foreign key(a,b) references t1(a) -------------- ERROR 1005 (HY000): Can't create table 'test.#sql-4856_1' (errno: 150) -------------- show warnings -------------- +-------+------+----------------------------------------------------+ | Level | Code | Message | +-------+------+----------------------------------------------------+ | Error | 1005 | Can't create table 'test.#sql-4856_1' (errno: 150) | +-------+------+----------------------------------------------------+ 1 row in set (0.00 sec) -----------------+ show engine innodb status; -----------------+ LATEST FOREIGN KEY ERROR ------------------------ 150730 15:15:57 Error in foreign key constraint of table test/#sql-4856_1: foreign key(a,b) references t1(a): Syntax error close to: 2015-07-30 13:44:35 7f30e1520700 Error in foreign key constraint of table tmp/#sql2612_2_2: foreign key(b) references t1(a): Cannot resolve table name close to: (a)
The error message is not clear and the foreign key error refers to an internal table name. In MariaDB 5.5.45 and 10.0.21 there is additional information:
create table t1(a int not null primary key, b int, key(b)) engine=innodb -------------- Query OK, 0 rows affected (0.14 sec) -------------- alter table t1 add foreign key(a,b) references t1(a) -------------- ERROR 1005 (HY000): Can't create table 'test.#sql-2b40_2' (errno: 150) -------------- show warnings -------------- +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 150 | Alter table `test`.`t1` with foreign key constraint failed. Foreign key constraint parse error in foreign key(a,b) references t1(a) close to ). Too few referenced columns, you have 1 when you should have 2. | | Error | 1005 | Can't create table 'test.#sql-2b40_2' (errno: 150) | +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
Incorrect cascading
A user may define a foreign key constraint with ON UPDATE SET NULL or ON DELETE SET NULL. However, this requires that the referenced columns are not defined as NOT NULL. Currently, the error message on this situation is:
create table t1 (f1 integer not null primary key) engine=innodb -------------- Query OK, 0 rows affected (0.40 sec) -------------- alter table t1 add constraint c1 foreign key (f1) references t1(f1) on update set null -------------- ERROR 1005 (HY000): Can't create table `test`.`#sql-2612_2` (errno: 150 "Foreign key constraint is incorrectly formed") -------------- show warnings -------------- +---------+------+-----------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-----------------------------------------------------------------------------------------------------+ | Error | 1005 | Can't create table `test`.`#sql-2612_2` (errno: 150 "Foreign key constraint is incorrectly formed") | | Warning | 1215 | Cannot add foreign key constraint | +---------+------+--------------------------------------------------------------------------------------------- --------+ show engine innodb status; --------+ LATEST FOREIGN KEY ERROR ------------------------ 2015-07-30 13:44:37 7f30e1520700 Error in foreign key constraint of table test/#sql-2612_2: foreign key (f1) references t1(f1) on update set null: You have defined a SET NULL condition though some of the columns are defined as NOT NULL.
Both error messages are not very useful, because the first does not really tell how the foreign key constraint is incorrectly formed and later does not say which column has the problem. This is improved in MariaDB 5.5.45 and 10.0.21:
create table t1 (f1 integer not null primary key) engine=innodb -------------- Query OK, 0 rows affected (0.10 sec) -------------- alter table t1 add constraint c1 foreign key (f1) references t1(f1) on update set null -------------- ERROR 1005 (HY000): Can't create table 'test.#sql-2b40_2' (errno: 150) -------------- show warnings -------------- +---------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 150 | Alter table `test`.`t1` with foreign key constraint failed. You have defined a SET NULL condition but column f1 is defined as NOT NULL in foreign key (f1) references t1(f1) on update set null close to on update set null. | | Error | 1005 | Can't create table 'test.#sql-2b40_2' (errno: 150) | +---------+------+---------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
Incorrect types
Column types for foreign key columns and referenced columns should match and use the same character set. If they do not, you currently get:
create table t1 (id int not null primary key, f1 int, f2 int, key(f1)) engine=innodb -------------- Query OK, 0 rows affected (0.47 sec) -------------- create table t2(a char(20), key(a), foreign key(a) references t1(f1)) engine=innodb -------------- ERROR 1005 (HY000): Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed") -------------- show warnings -------------- +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 150 | Create table 'test/t2' with foreign key constraint failed. There is no index in the referenced table where the referenced columns appear as the first columns. | | Error | 1005 | Can't create table `test`.`t2` (errno: 150 "Foreign key constraint is incorrectly formed") | | Warning | 1215 | Cannot add foreign key constraint | +---------+------+-----------------------------------------------------------------------------------------------------------------------------------------------------------------+ 3 rows in set (0.00 sec) --------+ show engine innodb status; --------+ LATEST FOREIGN KEY ERROR ------------------------ 2015-07-30 13:44:39 7f30e1520700 Error in foreign key constraint of table test/t2: foreign key(a) references t1(f1)) engine=innodb: 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/5.6/en/innodb-foreign-key-constraints.html for correct foreign key definition.
But do we have an index for the referenced column f1 in the table t2? So if there are multiple columns in both the foreign key column list and the referenced column list, where do we look for the error? In MariaDB 5.5.45 and 10.0.21 this is improved by:
create table t1 (id int not null primary key, f1 int, f2 int, key(f1)) engine=innodb -------------- Query OK, 0 rows affected (0.15 sec) -------------- create table t2(a char(20), key(a), foreign key(a) references t1(f1)) engine=innodb -------------- ERROR 1005 (HY000): Can't create table 'test.t2' (errno: 150) -------------- show warnings -------------- +---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Level | Code | Message | +---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ | Warning | 150 | Create table `test`.`t2` with foreign key constraint failed. Field type or character set for column a does not mach referenced column f1 close to foreign key(a) references t1(f1)) engine=innodb | | Error | 1005 | Can't create table 'test.t2' (errno: 150) | +---------+------+----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------+ 2 rows in set (0.00 sec)
Conclusions
There are several different ways to incorrectly define a foreign key constraint. In many cases when using earlier versions of MariaDB (and MySQL), the error messages produced by these cases were not very clear or helpful. In MariaDB 5.5.45 and 10.0.21 there are clearly improved error messages to help out the user. Naturally, there is always room for further improvements, so feedback is more than welcome!
References
- https://mariadb.atlassian.net/browse/MDEV-6697
- https://mariadb.atlassian.net/browse/MDEV-8524
This is another stupid error. It has to do with trying to successfully set foreign keys in MySQL.
ERROR 1005: Can’t create table (errno: 150)
Great, that’s fantastic. Here’s an example of where this error will occur.
CREATE TABLE main(
id INT UNSIGNED NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id)
);
CREATE TABLE other(
id INT UNSIGNED NOT NULL AUTO_INCREMENT,
main_id INT NOT NULL,
PRIMARY KEY(id),
FOREIGN KEY(main_id) REFERENCES main(id)
);
So I’m trying to make the table “other” reference the table “main” through the foreign key “main_id” and, if you try it, it’ll throw an Error 150.
Want the solution?
The foreign key “main_id” has to have the exact same type as the primary key that it references. In the example, “main_id” in the table “other” has the type INT NOT NULL while “id” in the table “main” has the type “INT UNSIGNED NOT NULL” and also AUTO_INCREMENT, but that isn’t something we have to worry about. To make things incredibly clear, here’s the working example.
CREATE TABLE main(
id INT UNSIGNED NOT NULL AUTO_INCREMENT,
PRIMARY KEY(id)
);
CREATE TABLE other(
id INT UNSIGNED NOT NULL AUTO_INCREMENT,
main_id INT UNSIGNED NOT NULL,
PRIMARY KEY(id),
FOREIGN KEY(main_id) REFERENCES main(id)
);
To solve ‘MySQL ERROR 1005: Can’t create table (errno: 150)‘ you likely just have to ensure that your foreign key has the exact same type as the primary key. Hope it helps.
If you’re working with SQL databases, you might have encountered error 1005 at some point in your development process. SQL error 1005 is a common error that occurs when attempting to create or modify a table in a database. It’s caused by various factors, such as incorrect syntax, data type mismatches, or foreign key constraints. But fear not! In this article, we will provide you with a comprehensive guide on how to fix SQL error 1005 and get your database back on track.
What is MySQL Error Code 1005?
SQL error 1005, also known as “Can’t create table (errno: 150)”, is a MySQL error that occurs when there is a problem with a foreign key constraint. Foreign key constraints are used to establish relationships between tables in a relational database. They ensure that data integrity is maintained by preventing actions that would create inconsistent or invalid data.
Possible Causes
When you encounter SQL error 1005, MySQL is telling you that there is an issue with a foreign key constraint while trying to create or modify a table. This error can be caused by a variety of reasons, such as:
- Incorrect syntax: The foreign key constraint might not be defined properly, leading to a syntax error in your SQL statement.
- Data type mismatch: The data types of the columns involved in the foreign key constraint must match exactly. If there is a mismatch in data types, MySQL will throw error 1005.
- Missing referenced table: The table referred to in the foreign key constraint might not exist in the database.
- Incompatible foreign key constraint: The referenced table might have a foreign key constraint with incompatible attributes, such as different collation, character set, or storage engine.
- Circular reference: A circular reference occurs when two or more tables reference each other with foreign key constraints, creating a loop. MySQL does not allow circular references, and it will result in error 1005.
Fix MySQL Error Code 1005
Now that we have a basic understanding of SQL error 1005 and its possible causes, let’s dive into the solutions to fix this issue.
- Check for typos or errors in your table definitions: Make sure that you have correctly defined your table columns, data types, and constraints. Double-check for any misspellings, missing or extra commas, and other syntax errors in your table definitions.
- Ensure that referenced columns and tables exist: If you are defining foreign key constraints, make sure that the referenced columns and tables actually exist in the database. If the referenced table has not been created yet, or if it has been dropped or renamed, you may encounter error code 1005.
- Check for conflicting constraints: If you have multiple foreign key constraints in your table definitions, ensure that there are no conflicts. For example, if you have two foreign keys that reference the same column in another table, MySQL will raise error code 1005. Make sure that your constraints are properly defined and do not conflict with each other.
- Verify data types and lengths: Make sure that the data types and lengths of the columns in your foreign key and referencing tables match exactly. Data type mismatches can result in error code 1005.
- Disable foreign key checks: You can temporarily disable foreign key checks in MySQL by running the following command before creating or modifying tables: SET FOREIGN_KEY_CHECKS = 0;. This can help you identify and fix any issues with foreign key constraints. However, be cautious when using this approach, as it can potentially lead to inconsistent data if not used properly.
- Check for circular references: If you have circular references in your foreign key constraints, where Table A references Table B and Table B references Table A, you will encounter error code 1005. To fix this issue, you may need to restructure your database schema to remove circular references.
- Check for storage engine compatibility: If you are using different storage engines for your referencing and referenced tables, you may encounter error code 1005. Make sure that the storage engines are compatible, such as using InnoDB for both tables, as some storage engines do not support foreign key constraints.
- Review MySQL error logs: Check the MySQL error logs for any additional information on the cause of the error. The error logs may provide more detailed information about the specific issue that is causing error code 1005.
By following these steps, you should be able to identify and fix the issue that is causing MySQL error code 1005. If you are still encountering issues, it may be helpful to consult the MySQL documentation or seek assistance from a knowledgeable database administrator.
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I am working as a Technical Architect in one of the top IT consulting firm. I have expertise on all versions of SQL Server since SQL Server 2000. I have lead multiple SQL Server projects like consolidation, upgrades, migrations, HA & DR. I love to share my knowledge. You can contact me on my social accounts for any consulting work.