Laravel migration - Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails

Question

I am trying to run a migration for a table inventories that I have created with this migration:

Schema::         


        

Answer 1

had the same problem. fixed it by adding nullable to field

Schema::create('table_name', function (Blueprint $table) {
    ...
    $table->integer('some_id')->unsigned()->nullable();
    $table->foreign('some_id')->references('id')->on('other_table');
    ...
});

note that after migration all existed rows will have some_id = NULL

Answer 2

You probably have some records in the inventories table with local_id that does not have corresponding id in the contents table, hence the error. You could solve it by one of the two ways:

• Run the migration with foreign_key_checks turned off. This will disabled the foreign key constraints for the existing rows (if that's what you want). It's documented here
• Insert only those records that have corresponding id field in contents table. You can use INSERT INTO.. WHERE EXISTS query to filter the records out, and insert only those records.