Laravel 5.5 ORM关联指定字段查询后orders_currency为空问题

Hey there, let's break down why your orders_currency relationship is returning empty even though you've selected the id field. Here are the most common culprits to check:

1. You're missing the foreign key in your select clause #

This is probably the biggest issue here. When Laravel loads related Order records, it needs the trip_id field to match against the parent Trip's id. Right now, your select() only includes id and converted_currency_code—you haven't included trip_id! Without that field, Laravel can't map which Order records belong to the current Trip, so it returns an empty collection.

Fix it by adding trip_id to your select:

public function orders_currency() {
    return $this->hasMany('App\Order', 'trip_id', 'id')
                ->select('id', 'trip_id', 'converted_currency_code');
}

2. Verify the foreign key and primary key match correctly #

Double-check these details:

• The orders table actually has a trip_id column (typos are easy to miss!)
• The data type of trip_id in orders matches the id type in trips (e.g., both are unsigned integers with the same length)
• There are actual Order records in your database where trip_id matches the id of the Trip instance you're working with. Run a quick raw SQL query to confirm:

  SELECT * FROM orders WHERE trip_id = [your_trip_id];
  

3. Check your model namespace (for Laravel 8+) #

If you're using Laravel 8 or newer, the default model namespace is App\Models, not App. So if your Order model lives in app/Models/Order.php, update your relationship to reference the correct namespace:

return $this->hasMany('App\Models\Order', 'trip_id', 'id')
            ->select('id', 'trip_id', 'converted_currency_code');

4. Soft deletes might be hiding records #

If your Order model uses the SoftDeletes trait, Laravel automatically excludes records marked as deleted. To test if this is the case, add withTrashed() to your relationship:

public function orders_currency() {
    return $this->hasMany('App\Order', 'trip_id', 'id')
                ->select('id', 'trip_id', 'converted_currency_code')
                ->withTrashed();
}

If records show up after this change, you know the issue was soft-deleted orders being filtered out.

5. Ensure you're loading the relationship correctly #

Make sure you're accessing the relationship properly:

• Eager loading: Use with('orders_currency') when fetching the Trip to load the relationship upfront:

  $trip = Trip::with('orders_currency')->find($tripId);
  

• Lazy loading: Access the relationship on an existing Trip model instance (not a query builder):

  $trip = Trip::find($tripId);
  $orders = $trip->orders_currency; // Triggers lazy loading
  

Trying to access the relationship directly on a query builder (like Trip::where('id', $tripId)->orders_currency) won't work—you need to fetch the actual model first.

内容的提问来源于stack exchange，提问作者Abeera