How to Resolve 'ERROR 1452: Cannot add or update a child row: a foreign key constraint fails'?

Troubleshooting "ERROR 1452: Cannot add or update a child row: a foreign key constraint fails"

This common database error, "ERROR 1452: Cannot add or update a child row: a foreign key constraint fails," arises when inserting data into a child table (ORDRELINJE) that has a foreign key referencing a parent table (Ordre). The error signifies a violation of referential integrity – the child table's foreign key doesn't match an existing primary key in the parent table.

In essence, the parent table (Ordre) contains primary data, while the child table (ORDRELINJE) contains foreign keys linking back to the parent. The foreign key constraint ensures data consistency by preventing orphaned records in the child table.

The error message indicates that the OrdreID you're trying to insert into ORDRELINJE doesn't exist in the Ordre table. This is because the database enforces the rule that all foreign keys must reference a valid record in the parent table.

Solution:

The solution is straightforward: ensure the corresponding record exists in the parent table (Ordre) before attempting to insert data into the child table (ORDRELINJE). Insert the necessary OrdreID into the Ordre table first. Only then will the foreign key constraint be satisfied, allowing you to successfully add the row to ORDRELINJE. Maintaining this order guarantees database integrity.

The above is the detailed content of How to Resolve 'ERROR 1452: Cannot add or update a child row: a foreign key constraint fails'?. For more information, please follow other related articles on the PHP Chinese website!