Cannot add foreign key constraint - Laravel 9 - laravel

Question

I have posts table:
Schema::create('posts', function (Blueprint $table) {
$table->id();
$table->unsignedBigInteger('imid');
$table->string('name');
$table->text('body');
$table->timestamps();
});
and
images table:
Schema::create('images', function (Blueprint $table) {
$table->id();
$table->unsignedBigInteger('imid');
$table->string('name')->nullable();
$table->longText('image_path')->nullable();
$table->timestamps();
});
I am trying to add a foreign field to existing posts table in a separate migration:
public function up()
{
Schema::table('posts', function (Blueprint $table) {
$table->foreign('imid')->references('imid')->on('images')->onDelete('cascade');
});
}
public function down()
{
Schema::table('posts', function (Blueprint $table) {
$table->dropColumn('imid');
});
}
But when I run
php artisan migrate
I get error:
SQLSTATE[HY000]: General error: 1215 Cannot add foreign key constraint (SQL: alter table `posts` add constraint `posts_imid_foreign` foreign key (`imid`) references `images` (`imid`) on delete cascade)
It seems I do it right. What am I missing here?

Answer 1

Check that both your tables have the columns for which you create the foreign key (imid) and that these columns have the same types. You can use the following commands to do this:
DESCRIBE posts;
DESCRIBE images;
Next, check if posts table has no imid values which point to non-existing records in the images table (If they are - connect them to existing ones or remove them)
SELECT posts.id, posts.imid FROM posts
LEFT JOIN images ON posts.imid = images.imid
WHERE images.id IS NULL;
Make sure your tables are using InnoDB engine
SHOW TABLE STATUS WHERE name = 'posts';
if Engine != InnoDB then run:
ALTER TABLE posts ENGINE = InnoDB;
Finally, I suggest that you change the down method of your migration so that it does the reverse of the up method:
Schema::table('posts', function (Blueprint $table) {
$table->dropForeign('posts_imid_foreign');
});