Change foreign key without losing data in column - laravel

Question

I've checked google, but I haven't found a way to preserve data while changing a foreign key on a table.
I have two tables, User Events and User Sports
Table User Events
+--------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+--------------+------------------+------+-----+---------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| date | date | YES | | NULL | |
| description | text | YES | | NULL | |
| user_id | int(10) unsigned | YES | MUL | NULL | |
| sport_id | int(10) unsigned | YES | MUL | NULL | |
| created_at | timestamp | YES | | NULL | |
| updated_at | timestamp | YES | | NULL | |
| deleted_at | timestamp | YES | MUL | NULL | |
+--------------+------------------+------+-----+---------+----------------+
Table User Sports
+------------------+------------------+------+-----+---------+----------------+
| Field | Type | Null | Key | Default | Extra |
+------------------+------------------+------+-----+---------+----------------+
| id | int(10) unsigned | NO | PRI | NULL | auto_increment |
| name | varchar(191) | NO | | NULL | |
| default_sport_id | int(10) unsigned | YES | UNI | NULL | |
| user_id | int(11) | YES | | NULL | |
| created_at | timestamp | YES | | NULL | |
| updated_at | timestamp | YES | | NULL | |
| deleted_at | timestamp | YES | | NULL | |
+------------------+------------------+------+-----+---------+----------------+
Before creating User Sports table, in table User Events I had foreign sport_id from Sports table.
Now, when I want to change that column to be foreign key from Sports to User Sports table I'm getting this message on php artisan migrate:
SQLSTATE[23000]: Integrity constraint violation: 1452 Cannot add or update a child row: a foreign key constraint fails
The migration works if I drop the column sport_id from User Events but I don't want data loss.
Here is my migration:
public function up()
{
Schema::table('user_events', function (Blueprint $table) {
$table->dropForeign('event_sport_id');
});
Schema::table('user_events', function (Blueprint $table) {
$table->foreign('sport_id')
->references('default_sport_id')
->on('user_sports')
->onDelete('set null');
});
}
Can someone point me in the right direction?
Thanks

Answer 1

You must pass an array not a string to the method dropForeign: $table->dropForeign(['event_sport_id']);