Top 36 Errno 150 Foreign Key Constraint Is Incorrectly Formed 23645 Good Rating This Answer

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How do I fix mysql error 150?

Altering a table returns an error (errno: 150) if a foreign key definition is incorrectly formed for the altered table. Dropping an index required by a foreign key constraint. The foreign key constraint must be removed before dropping the index.

What are foreign key constraint?

The FOREIGN KEY constraint is used to prevent actions that would destroy links between tables. A FOREIGN KEY is a field (or collection of fields) in one table, that refers to the PRIMARY KEY in another table.

How do I create a foreign key in MariaDB?

In this syntax: First, specify the name of the foreign key constraint after the constraint keyword. MariaDB will implicitly assign a generated name if you skip the constraint clause. Second, specify the name of the foreign key followed by a list of comma-separated column names placed within parentheses.

How do I reference a foreign key in mysql?

Following are the syntax of the ALTER TABLE statement to add a foreign key in the existing table:

ALTER TABLE table_name.
ADD [CONSTRAINT [symbol]] FOREIGN KEY.
[index_name] (column_name, …)
REFERENCES table_name (column_name,…)
ON DELETE referenceOption.
ON UPDATE referenceOption.

How do I delete a foreign key constraint in MySQL?

You can drop a foreign key constraint using the following ALTER TABLE syntax: ALTER TABLE tbl_name DROP FOREIGN KEY fk_symbol; If the FOREIGN KEY clause defined a CONSTRAINT name when you created the constraint, you can refer to that name to drop the foreign key constraint.

How do I delete a foreign key constraint in SQL?

To delete a foreign key constraint

In Object Explorer, expand the table with the constraint and then expand Keys.
Right-click the constraint and then click Delete.
In the Delete Object dialog box, click OK.

How do I find foreign key constraints in SQL Server?

Using SQL Server Management Studio

Open the Table Designer for the table containing the foreign key you want to view, right-click in the Table Designer, and choose Relationships from the shortcut menu.
In the Foreign Key Relationships dialog box, select the relationship with properties you want to view.

How would you add a foreign key constraint?

To create a SQL foreign key constraint, the parent table should have primary key column or column with UNIQUE constraint. In this case, table Dept is parent table which has Primary key and will be referenced in child tables having foreign key.

What is not true about foreign key?

Q 26 – Which of the following is not true about a FOREIGN KEY constraint? A – It is a referential integrity constraint. B – It establishes a relationship between a primary key or a unique key in the same table or a different table. C – A foreign key value cannot be null.

Does MariaDB support foreign key?

Foreign keys have the following limitations in MariaDB: Currently, foreign keys are only supported by InnoDB. Cannot be used with views. The SET DEFAULT action is not supported.

How do I find my foreign key in MariaDB?

In above syntax first, we use create table statement after that we constraint name to specify the foreign key name, if we skip this constraint the MariaDB will use the default generated name. In the next part foreign key followed by a foreign name with a list of column names separated by a comma within parentheses.

Can not add foreign key constraint?

The usual cause are generally a mismatch in the type of the column of the primary table and the foreign table. It can also be a mismatch in the Engine type of two tables i.e. MyISAM or InnoDB. Datatype both columns should have same datatype. int(11) on one table and smallint(5) on another will cause problem.

Where is foreign key constraint in MySQL?

select * from INFORMATION_SCHEMA. TABLE_CONSTRAINTS where CONSTRAINT_TYPE = ‘FOREIGN KEY’; You can view all constraints by using select * from information_schema.
…

To see all FKs in your table: USE ‘<yourschema>’; SELECT i. …
To see all the tables and FKs in your schema: …
To see all the FKs in your database:

How do I add a foreign key constraint in MySQL using alter command?

Here’s the syntax to create foreign key in MySQL. ALTER TABLE table_name ADD CONSTRAINT constraint_name FOREIGN KEY (foreign_key_name,…) REFERENCES parent_table(column_name,…); In the above query, table_name is the the table where you want to add foreign key.

How do I view constraints in MySQL?

select COLUMN_NAME, CONSTRAINT_NAME, REFERENCED_COLUMN_NAME, REFERENCED_TABLE_NAME from information_schema. KEY_COLUMN_USAGE where TABLE_NAME = ‘yourTableName’; To display all constraints on a table, implement the above syntax.

Why can’t I create table in SQL?

usually, the mismatch between foreign key & primary key causes the error:150. The foreign key must have the same datatype as the primary key. Also, if the primary key is unsigned then the foreign key must also be unsigned.

How does InnoDB check engine status?

SHOW ENGINE INNODB STATUS is a specific form of the SHOW ENGINE statement that displays the InnoDB Monitor output, which is extensive InnoDB information which can be useful in diagnosing problems.

What is on delete cascade?

Use the ON DELETE CASCADE option to specify whether you want rows deleted in a child table when corresponding rows are deleted in the parent table. If you do not specify cascading deletes, the default behavior of the database server prevents you from deleting data in a table if other tables reference it.

Solve MySQL Error : (errno: 150 \”Foreign key constraint is incorrectly formed\”)

sql – mysql Foreign key constraint is incorrectly formed error – Stack Overflow

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Summary of article content: Articles about sql – mysql Foreign key constraint is incorrectly formed error – Stack Overflow I ran into this same problem with HeiSQL. The error you receive is very cryptic. My problem ended up being that the foreign key column and … …
Most searched keywords: Whether you are looking for sql – mysql Foreign key constraint is incorrectly formed error – Stack Overflow I ran into this same problem with HeiSQL. The error you receive is very cryptic. My problem ended up being that the foreign key column and …
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Summary of article content: Articles about mariadb – MySQL FOREIGN KEY constraint is incorrectly formed – Database Administrators Stack Exchange The table you’re referencing is not created (not the case); The table you’re referencing is not InnoDB (not the case, both notification and … …
Most searched keywords: Whether you are looking for mariadb – MySQL FOREIGN KEY constraint is incorrectly formed – Database Administrators Stack Exchange The table you’re referencing is not created (not the case); The table you’re referencing is not InnoDB (not the case, both notification and …
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Summary of article content: Articles about errno 150 foreign key constraint is incorrectly formed Check the order of your migrations. If your migrate command is trying to make the posts table before the post_categories table this will occur with MySQL. It … …
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errno 150 foreign key constraint is incorrectly formed

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Summary of article content: Articles about Khắc phục lỗi “Foreign key constraint is incorrectly formed” QA Bug Lỗi “Foreign key constraint is incorrectly formed” có rất nhiều nguyên … sql-798_ffe95d’ (errno: 121) Duplicate key on write or update. …
Most searched keywords: Whether you are looking for Khắc phục lỗi “Foreign key constraint is incorrectly formed” QA Bug Lỗi “Foreign key constraint is incorrectly formed” có rất nhiều nguyên … sql-798_ffe95d’ (errno: 121) Duplicate key on write or update. Lỗi “Foreign key constraint is incorrectly formed” có rất nhiều nguyên nhân xảy ra như loại column không match với nhau, tên của khóa ngoại …
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Summary of article content: Articles about SQL FOREIGN KEY ERROR (errno: 150 “Foreign key constraint is incorrectly formed”) SQL FOREIGN KEY ERROR (errno: 150 “Foreign key constraint is incorrectly formed”) … The problem is that you have the company table reference the … …
Most searched keywords: Whether you are looking for SQL FOREIGN KEY ERROR (errno: 150 “Foreign key constraint is incorrectly formed”) SQL FOREIGN KEY ERROR (errno: 150 “Foreign key constraint is incorrectly formed”) … The problem is that you have the company table reference the … Foreign keys – The problem is that you have the company table reference the branch and contact table before they are created. Also, the branch table references the contact table and vice versa so the database goes like that: Creating the contact table … there is a bid field connected to a table named branch … table branch does not exist -> error You have to create the contact table first but without the foreign id reference to bid, then create branch table and then company table. After you have your tables all set you can execute another query to add a foreign id reference to bid. So Like this: CREATE TABLE contact( contact_id INT(15) NOT NULL AUTO_INCREMENT UNIQUE, fst_name varchar(20), mdl_name varchar(20), lst_name varchar(20), sex varchar(20), dob DATE, phone_number INT(15), address varchar(255), email varchar(255), bid INT(15) NOT NULL UNIQUE, PRIMARY KEY (contact_id) )ENGINE=InnoDB; CREATE TABLE branch( branch_id INT(15) NOT NULL AUTO_INCREMENT UNIQUE, branch_type varchar(30), cid INT(15) NOT NULL UNIQUE, PRIMARY KEY (branch_id), FOREIGN KEY (cid) REFERENCES contact(contact_id) ); CREATE TABLE company( company_name varchar(30) UNIQUE NOT NULL, bid INT(15) NOT NULL UNIQUE, cid INT(15) NOT NULL UNIQUE, FOREIGN KEY (bid) REFERENCES branch(branch_id), FOREIGN KEY (cid) REFERENCES contact(contact_id) ); Notice I removed FOREIGN KEY (bid) REFERENCES branch (branch_id) And then: ALTER TABLE contact ADD FOREIGN KEY (bid) REFERENCES branch(branch_id); P.S Run the commands in the same order
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Answer

mysql Foreign key constraint is incorrectly formed error

Although the other answers are quite helpful, just wanted to share my experience as well.

I faced the issue when I had deleted a table whose id was already being referenced as foreign key in other tables (with data) and tried to recreate/import the table with some additional columns.

The query for recreation (generated in phpMyAdmin) looked like the following:

CREATE TABLE `the_table` ( `id` int(11) NOT NULL, /* No PRIMARY KEY index */ `name` varchar(255) NOT NULL, `name_fa` varchar(255) NOT NULL, `name_pa` varchar(255) NOT NULL ) ENGINE=InnoDB DEFAULT CHARSET=utf8; … /* SOME DATA DUMP OPERATION */ ALTER TABLE `the_table` ADD PRIMARY KEY (`id`), /* PRIMARY KEY INDEX */ ADD UNIQUE KEY `uk_acu_donor_name` (`name`);

As you may notice, the PRIMARY KEY index was set after the creation (and insertion of data) which was causing the problem.

Solution

The solution was to add the PRIMARY KEY index on table definition query for the id which was being referenced as foreign key, while also removing it from the ALTER TABLE part where indexes were being set:

MySQL FOREIGN KEY constraint is incorrectly formed

I have the following table definition:

CREATE TABLE `async_task` ( `idasync_task` bigint(20) unsigned NOT NULL AUTO_INCREMENT, `idasync_type` int(10) unsigned NOT NULL, `priority` tinyint(3) NOT NULL, `status` enum(‘todo’,’doing’,’failed’) NOT NULL DEFAULT ‘todo’, `iduser` int(11) NOT NULL, `date_added` datetime NOT NULL, PRIMARY KEY (`idasync_task`), KEY `priority_id` (`priority`,`idasync_task`), KEY `status_type` (`status`,`idasync_type`) ) ENGINE=InnoDB AUTO_INCREMENT=1 DEFAULT CHARSET=utf8;

I’ve added a column to the my notification table which I want to point to async_task :

ALTER TABLE `notification` ADD COLUMN `async_task_id` BIGINT(20)

And when I add the following foreign key:

ALTER TABLE `notification` ADD CONSTRAINT `fk_notification_async_task` FOREIGN KEY (`async_task_id`) REFERENCES `async_task`(`idasync_task`);

I get:

ERROR 1005 (HY000): Can’t create table `my_database`.`#sql-182_2d` (errno: 150 “Foreign key constraint is incorrectly formed”)

I’ve looked elsewhere but only find the errors as being:

The table you’re referencing is not created (not the case) The table you’re referencing is not InnoDB (not the case, both notification and async_task are InnoDB) You’re not referencing the entire primary key (not the case, the only primary key is the ID column).

What else could it be?

Khắc phục lỗi “Foreign key constraint is incorrectly formed” QA Bug

Lỗi “Foreign key constraint is incorrectly formed” có rất nhiều nguyên nhân xảy ra như loại column không match với nhau, tên của khóa ngoại (Foreign key) không phải là duy nhất, bạn không thể tạo khóa ngoại với ON UPDATE SET NULL nếu cột không cho phép giá trị NULL …

Hướng dẫn xử lý Foreign key constraint is incorrectly formed

Nguyên nhân 1: Type column không khớp với nhau

Đây là nguyên nhân rõ ràng nhất. Nếu bạn cố gắng tạo khóa ngoại từ cột INT(10) sang cột SMALLINT(5) , bạn sẽ gặp lỗi ở trên.

Chỉ cần đảm bảo rằng các loại cột giống hệt nhau, bao gồm cả UNSIGNED flag.

Nguyên nhân 2: Tên khóa ngoại không phải duy nhất

Bạn có tin hay không, nhưng tên của các khóa ngoại phải là duy nhất trong cùng một cơ sở dữ liệu. Tùy thuộc vào phiên bản MySQL của bạn, bạn có thể gặp lỗi:

Can’t create table ‘mydatabase.#sql-798_ffe95d’ (errno: 121) Duplicate key on write or update

Nguyên nhân thứ 3: Không thể ON DELETE hay ON UPDATE

Bạn không thể tạo khóa ngoại với ON UPDATE SET NULL nếu cột không cho phép giá trị NULL .

Xem thêm.

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Top 36 Errno 150 Foreign Key Constraint Is Incorrectly Formed 23645 Good Rating This Answer

How do I fix mysql error 150?

What are foreign key constraint?

How do I create a foreign key in MariaDB?

How do I reference a foreign key in mysql?

How do I delete a foreign key constraint in MySQL?

How do I delete a foreign key constraint in SQL?

How do I find foreign key constraints in SQL Server?

How would you add a foreign key constraint?

What is not true about foreign key?

Does MariaDB support foreign key?

How do I find my foreign key in MariaDB?

Can not add foreign key constraint?

Where is foreign key constraint in MySQL?

How do I add a foreign key constraint in MySQL using alter command?

How do I view constraints in MySQL?

Why can’t I create table in SQL?

How does InnoDB check engine status?

What is on delete cascade?

sql – mysql Foreign key constraint is incorrectly formed error – Stack Overflow

mariadb – MySQL FOREIGN KEY constraint is incorrectly formed – Database Administrators Stack Exchange

errno 150 foreign key constraint is incorrectly formed

Khắc phục lỗi “Foreign key constraint is incorrectly formed” QA Bug

MySQL :: MySQL 8.0 Reference Manual :: 13.1.20.5 FOREIGN KEY Constraints

SQL FOREIGN KEY Constraint

MySQL Foreign Key – javatpoint

SQL FOREIGN KEY ERROR (errno: 150 “Foreign key constraint is incorrectly formed”)

Laravel Errno 150 Foreign Key Constraint Is Incorrectly Formed

MySQL :: MySQL 8.0 Reference Manual :: 13.1.20.5 FOREIGN KEY Constraints

Mysql – Laravel migration (errno: 150 “Foreign key constraint is incorrectly formed”) – iTecNote

mysql Foreign key constraint is incorrectly formed error

MySQL FOREIGN KEY constraint is incorrectly formed

Khắc phục lỗi “Foreign key constraint is incorrectly formed” QA Bug

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