Foreign key constraint is incorrectly formed (Laravel Migration)

Question

As written in the error logs, maybe the error is caused different forms in the reference table and parent table but I still don't understand cause I'm new in programming

here table 1

<?php

Schema::create('questions', function (Blueprint $table) {
    $table->id();
    $table->string('question');
    $table->unsignedInteger('quiz_id');
    $table->timestamps();
});

here table 2

<?php

Schema::create('answers', function (Blueprint $table) {
    $table->id();
    $table->unsignedInteger('question_id');
    $table->string('answer');
    $table->boolean('is_correct');
    $table->timestamps();
});

Schema::table('answers', function (Blueprint $table){
    $table->foreign('question_id')->references('id')->on('questions')->onDelete('cascade');
});

what should I change in this code? thanks

unclexo · Accepted Answer · 2020-07-02T17:17:10.807

4

As of Laravel 5.8 $table->id() is an alias of $table->bigIncrements('id') which sets the id column's data type to unsigned BIGINT under the hood.

In the answers table, you've $table->unsignedInteger('question_id'); which is equivalent to unsigned INT/INTEGER data type and that is not compatible with what $table->id() represents in the questions table. So you have to change the data type of question_id column to unsigned BIGINT in the answers table.

And to do that, you need to use Blueprint::unsignedBigInteger() method to make the question_id column's data type unsigned BIGINT as you're setting it up as a foreign key.

So use

$table->unsignedBigInteger('question_id');

Instead of

$table->unsignedInteger('question_id');

edited Jul 02 '20 at 17:17

answered Jul 02 '20 at 15:51

unclexo

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@FebriTahta do NOT forget to mark the answer correct that helped you here. :) – unclexo Jul 02 '20 at 17:19
yes sir.. thanks for ur answer, i got typo in my command before, im deleted. im already mark this answer correct. :) thankyou – Febri Tahta Jul 02 '20 at 20:39

score 1 · Answer 2 · answered Jul 02 '20 at 15:52

1

Be Careful: Laravel 5.8 Added bigInteger for foreign key ( As Defaults)

In your foreign key column do bigInteger() instead of integer().

$table->unsignedBigInteger('question_id');

answered Jul 02 '20 at 15:52

STA

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thanks sir now im understand :) – Febri Tahta Jul 02 '20 at 20:37

score 1 · Answer 3 · answered Jul 02 '20 at 15:52

1

$table->id(); is alias of $table->bigIncrements('id') so you should use $table->unsignedBigInteger('question_id');

answered Jul 02 '20 at 15:52

Ahmad

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thanks for ur answer sir – Febri Tahta Jul 02 '20 at 20:37

Foreign key constraint is incorrectly formed (Laravel Migration)

3 Answers3