Techniques to Fix Error Code 1451 MySQL

MySQL Error 1451 is an error that can be fixed without any prior technical know-how. It is also sometimes called the foreign key constraint error. You can solve this issue even if you have the basic information about MySQL. However, if you do not make yourself familiar with the concepts and the reasons for the error, you will not be able to fix the error.

MySQL is an open-source relational database software developed to manage the data in different forms. It also allows various operations on the data, like linking an entry of one table to another table. The interlinking of this kind is carried out using a foreign key.

The different tables are used here as per their applicability. There is a child table in which the foreign key is present that carries out the interlinking. Besides, there is also a parent table that gives all the references. The error 1451 arises in my SQL if any task executed on an entry is utilized as a reference for some other table. The error can also occur in the form of a foreign key constraint error.

In this blog, we will guide you to fix Error 1451 in MySQL database Cannot delete or update a parent row: a foreign key constraint fails. But before that, let us go through the reasons that generate the MySQL error code 1451.

Reasons for Error Code 1451 My SQL

MySQL Error 1451 arises due to several reasons. The most common reasons for the error are discussed below.

  • One of the main causes of this error is the deletion of an entry from the parent table. In doing so, the primary key gets linked to the foreign key of the child table. If you delete it directly, the error pops up.
  • The difference in the data type of both the parent and child table creates this error. It should be the same for both tables. For example, if the data type of the primary table is .int, then the foreign key in the child table should also be .int.
  • The data is stored in different ways in MySQL. The character set or collations is the way the data is stored. The error code 1451 MySQL is generated if the collation of both the child and parent tables of the columns is not the same. Thereby, the collations for both should be the same, be it utf-8 or any other.
  • Error Code 1451 MySQL can also pop up if the signing definitions of the two columns are different. The unsigned option under the details of both the key should be the same to avoid this error.

Solution to Fix Error Code 1451 MySQL

Cannot delete or update a parent row: a foreign key constraint fails can be generated if the correct sequence of the tasks is not followed while deleting the entries from the parent table. The below error pops up on the screen.

Error 1451 – cannot delete or update a parent row: a foreign key constraint fails

Hence, to prevent this error, the user should try to first delete or drop the foreign key and then, delete the primary key.

Below mentioned methods are described in a stepwise manner to delete the foreign key of the child table and resolve MySQL error 1451.

Method – 1

By following this method, you will be able to delete the foreign key of the child table. The steps are mentioned briefly for your execution.

  1. Delete the foreign key from the child table by entering the following command.

mysql> DELETE FROM (Child_table_Name)

Where (Row_Name) = (Foreign_key)

  1. Repeat the process as per your required entries in the child table.
  2. Now, type the below entry to check the leftover elements in the Child table.

mysql> select * (Child_table_Name)

  1. After that, remove the Primary key from the Parent table with the help of the below command.

mysql> DELETE FROM (Parent_table_Name)

Where (Row_Name) = (Primary_key)

  1. Check the Parent table through the following command.

mysql> SELECT * (Parent_table_Name)

Method – 2

The child table foreign key can also be deleted using the below commands to be entered into MySQL.

  1. Open MySQL and enter the following command.

mysql> ALTER TABLE (Child_table_Name)

DROP FOREIGN KEY (Foreign_Key_Entry)

  1. Enter the same command for every desired foreign key as per your need.
  2. The FOREIGN KEY command is not supported on every MySQL. Therefore, you can use the CONSTRAINT command.
  3. After that, type the below command to delete the primary key from the table.

mysql> DELETE FROM (Parent_table_Name)

Where (Row_Name) = (Primary_key)

Occasionally, the error code 1451 MySQL is not developed due to any of the above-mentioned reasons. It arises due to the corruption present in the files. If the manual methods discussed above do not solve your error or you find them complex and time-consuming, you can go for an alternate solution. The professional method, MySQL Database Recovery, is an automatic method that recovers all the SQL files and can resolve any error. It repairs the damaged files that cause the errors. Also, this MySQL recovery tool fix MySQL error 1045 (28000) access denied for users.


Here, we have analyzed the reasons that give rise to the error code 1451 MySQL. The error can be resolved by the manual methods that have been discussed. These manual methods fix ERROR 1451: Cannot delete or update a parent row: a foreign key constraint fails. Moreover, these methods are not apt for some users and are not always effective. So, you can directly opt for a professional solution to recover the corrupt database files and it also fix errors like MySQL error 1451, MySQL 1146 table does not exist error. Thanks for reading this blog. I hope you found it helpful.

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About The Author:

Mithilesh Tata is a technical expert who has assisted thousands of clients with Microsoft Outlook and other cloud-based email clients. He enjoys writing on email clients backup as well as email migration. He is always excited about giving troubled readers the most up-to-date knowledge, explanation, and user-friendly solutions.

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