Why Am I Getting a MySQL Foreign Key Constraint Failure (Error Code 1452)?

MySQL foreign key constraint failed: error code 1452

While trying to insert a value into the ORDRELINJE table in a MySQL database, an error occurred with the message "Error code: 1452. Unable to add or update child row: Foreign key constraint failed".

Understanding foreign key constraints

Foreign key constraints ensure referential integrity in relational databases. A foreign key is a column in a child table that references a primary key column in the parent table. When a row is inserted or updated in the child table, the value of the foreign key must match an existing value in the primary key column of the parent table.

Error analysis

In this case, the error indicates that the ORDRELINJE table has a foreign key constraint that references the Ordre table. When trying to insert a row into the ORDRELINJE table, the value of the Ordre column does not match any existing row in the Ordre table.

Resolving errors

To resolve this error, make sure the following conditions are met:

1. Matching rows in parent table: The value of the Ordre column in the ORDRELINJE table should match the existing value of the OrdreID column in the Ordre table. If necessary, first insert the corresponding rows into the Ordre table.
2. Data type compatibility: The data types of the foreign key column (Ordre) and the primary key column it references (OrdreID) must match.
3. Cascading behavior: Configure a foreign key constraint to allow rows to be inserted into a child table even if there are no matching rows in the parent table. This can be achieved by using the ON DELETE CASCADE or ON UPDATE CASCADE option when creating the foreign key constraint.

The above is the detailed content of Why Am I Getting a MySQL Foreign Key Constraint Failure (Error Code 1452)?. For more information, please follow other related articles on the PHP Chinese website!