MySQL Error 1452: How to Resolve Foreign Key Constraint Failures?

MySQL foreign key constraint error: ERROR 1452

MySQL error "ERROR 1452: Cannot add or update a child row: a foreign key constraint fails" usually occurs when trying to insert or update a row in a child table without a matching foreign key value in the parent table.

Database Schema

In the given database schema, the ORDRELINJE table has a foreign key constraint that references the ORDERID column in the ORDRE table, and another foreign key constraint that references the PRODUKTID column in the PRODUKT table.

Foreign key constraint conflict

When trying to insert a row into the ORDRELINJE table, the system checks whether the values ​​of the ORDER and PRODUKT columns match the values ​​of the existing rows in the ORDRE and PRODUKT tables respectively. This error is triggered if no matching row is found.

Solution

To resolve this error, ensure that the ORDERID and PRODUKTID values ​​in the ORDRELINJE table correspond to existing rows in the ORDRE and PRODUKT tables. Before inserting ORDRELINJE, insert the corresponding rows in ORDRE and PRODUKT.

Example

For example, if you try to insert a row with ORDERID = 100 and PRODUKTID = 200 into the ORDRELINJE table, first check if a row with ORDERID = 100 exists in the ORDRE table, and if a row with PRODUKTID = 200 exists in the PRODUKT table. If any row does not exist, insert that row before trying to insert ORDRELINJE.

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