Selecting a non-foregin column with eloquent "with"

Question

I have two model (Event and Occurence) with db tables that are linked by a relationship:

*events:*
 $table->id();
 $table->unsignedBigInteger('institution_id');
 $table->time('start_time', 0);
 $table->time('end_time', 0);
 $table->timestamps();
 $table->softDeletes();

and

*event_occurence:*
$table->id();
$table->unsignedBigInteger('event_id');
$table->date('occurs_at');

$table->foreign('event_id')
  ->references('id')
  ->on('events');

Then

In Event class:

public function occurences()
{
    return $this->hasMany(Occurence::class);
}

Now, I'm tring to get back the 'occurs_at' field in an array when I do an Eloquent call by using a scope. Here is the scope function:

public function scopeWithDates($query)
{
    $query->with('occurences:occurs_at');
}

And here is my call:

$events = Event::withDates()->get();
return $events;

When I do this, my occurences object on the return is empty. But, when I do:

public function scopeWithDates($query)
{
    $query->with('occurences:event_id');
}

I get the event IDs. Why? Can you only do ->with and select specific columns on foreign keys?

Answer 1

You can select specific columns, but you always have to specify the foreign key.

Get Specific Columns Using “With()” Function in Laravel Eloquent

Answer 2

While getting specific record from laravel relationship, you have to specify the foreign key and then other fields.

$query->with('occurences:event_id,occurs_at');

And I haven't tested it in Scope but it may also work in this way

$query->with(['occurences' => function($record){
   $record->select('event_id','occurs_at');
}]);