Simple Ways to Fix Error Code 1451 MySQL

Error code 1451 MySQL is a simple issue to fix. It does not require deep technical knowledge to resolve this issue. However, if you don’t the reasons and some key concepts, you will not be able to fix this error message. So, let’s learn some basics of MySQL.

MySQL is a relational database software designed to manage data in various forms. You can also perform various operations on this data. One such feature is linking an entry of one table to some other entry of another table. This method is performed using a foreign key.

The two tables used here are the Parent table and child table. The table in which the foreign key is available is known as the child table and the table from which the reference is taken is known as the parent table. If you perform any action on an entry that is used as a reference of some other table, you will face a foreign key constraint error or MySQL error 1451,

You will learn how to delete any entry so that this issue will never arise. But before, you need to know some other reasons for MySQL 1451 error.

Why does this error arise?

You can fix the error code 1451 MySQL easily. This error is caused by various reasons but some reasons are more prominent than others. They appear in most cases. Before jumping to the methods to resolve this issue, you need the know the major reasons for this error.

  • The first and most often reason for this error is when you try to delete an entry from the parent table. The primary key will get linked to the foreign key of the child table. You can not delete it directly. Otherwise, the foreign key constraint error will appear on the screen.
  • The data type of both the parent table and child table are not the same. If the data type of the primary key in the parent table is .int, the foreign key in the child table must have .int data type.
  • Error code 1451 MySQL also arises when the collation of columns of both parent and child tables are different. Collation or character set means how the data is sorted. So, if you select utf-8 for the primary key, the collation of the foreign key must also be utf-8.
  • If the signing definition of these two columns is different, the foreign key constraint error occurs in MySQL. When you open the details of the primary and foreign key you will see an option of unsigned. It must be the same for both keys.

Also Read: How to Unlock Microsoft SQL Server User Accounts Easily

Methods to Fix Error code 1451 MySQL

The error code 1451 MySQL or foreign key error arises because you are not following the correct order. If you are trying to delete an entry from the parent table which is used as a foreign key in some other table, you will see the following text on the screen.

#ErrorCode 1451 – can’t delete or update a parent row: a foreign key constraint fails

So, you should first delete or drop the foreign key. After that, you can delete the primary key.

Following are the methods to delete the foreign key of the child table:

#Method 1

  1. First, delete the foreign key from the child table by using the following command:
mysql> DELETE FROM (Child_table_Name)             Where (Row_Name) = (Foreign_key)
  1. Repeat the process for desired entries in the child table.
  2. After that, Enter the following entry to check the remaining elements in the Child table:
mysql> select * (Child_table_Name)
  1. Delete the Primary key from the Parent table using the following command:
mysql> DELETE FROM (Parent_table_Name)            Where (Row_Name) = (Primary_key)
  1. Check the Parent table by using the following command:
mysql> SELECT * (Parent_table_Name)

# Method 2

  1. Give the following command in MySQL:
mysql> ALTER TABLE (Child_table_Name)            DROP FOREIGN KEY (Foreign_Key_Entry)
  1. Repeat the command for every desired foreign key.
  2. Some MySQL does not support the FOREIGN KEY command, so you can use CONSTRAINT instead.
  3. Give the following command to delete the primary key from the table
mysql> DELETE FROM (Parent_table_Name)            Where (Row_Name) = (Primary_key)

Sometimes, the error code 1451 MySQL does not arise due to any of the above reasons. It may be due to file corruption. Now, you can repair the MySQL database files using manual methods, but they are difficult and time-consuming. Also, these methods are not completely reliable. So, the best solution to this problem is an automatic method. MysQL Database Recovery Software is a suitable utility that repairs the damaged data files.

Conclusion

The error code 1451 MySQL appears a tough error but it can be resolved easily. It generally arises when you want to delete an entry from the parent table which is a reference for another table. There are also some other reasons. So, the best way to solve the issue is to delete the foreign key from the child table first. Then, you can perform any operation of the primary key of the parent table.

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