Laravel migration: “Foreign key constraint is incorrectly formed” (errno 150)

Question

When migrating my DB, this error appears. Below is my code followed by the error that I am getting when trying to run the migration.

Code

Answer 1

I just use $table->unsignedBigInteger('user_id'); and solve it . (laravel 5.8)

Answer 2

It is a simple question, so give a simple answer and stop beating about the bush, change your example $table->integer('user_id')->unsigned(); to $table->BigInteger('user_id')->unsigned(); to solve the foreign key error. so change integer to BigInteger in the migration file...

Answer 3

1. Check in your database reference table must have primary key && auto increment
2. Drop the table which you want to migrate and Run the migrate again

Answer 4

Maybe it can be of help to anyone landing here : I just experienced this same issue, and in my case it was that I had a (composite) unique constraint set on the foreign key column BEFORE the foreign key constraint. I resolved the issue by having the "unique" statement placed AFTER the "foreign" statement.

Works:

$table->foreign('step_id')->references('id')->on('steps')->onDelete('cascade');
$table->unique(['step_id','lang']);

Doesn't work:

$table->unique(['step_id','lang']);
$table->foreign('step_id')->references('id')->on('steps')->onDelete('cascade');

Answer 5

For me everything was in correct order, but it still didn't work. Then I found out by fiddling that the primary key must be unsigned.

//this didn't work
$table->integer('id')->unique();
$table->primary('id');

//this worked
$table->integer('id')->unsigned()->unique();
$table->primary('id');

//this worked 
$table->increments('id');

Answer 6

In my case, the new laravel convention was causing this error.

Just by a simple swap of the table creation id did the trick.

$table->increments('id'); // ok

, instead of:

$table->bigIncrements('id'); // was the error.

Already working with Laravel v5.8, never had this error before.