Eloquent多对多关系中的Sum pivot表字段

Question

I have an orders table, an items table, and a pivot table called item_order which has two custom fields ( price , quantity ). The relationship between Order and Item is belongsToMany. I'm trying to return the count of all items with an id of 1 , where the parent Order->status == 'received' . For the life of me, I can't figure out how to do this.

class Order extends Model
{
    public function items()
    {
        return $this->belongsToMany(Item::class)->withPivot('price', 'quantity');
    }
}

class Item extends Model
{
    public function orders()
    {
        return $this->belongsToMany(Order::class)->withPivot('price', 'quantity');
    }
}

Answer 1

Try this:

$total_quantity = Item::find(1) // getting the Item
    ->orders() // entering the relationship
    ->with('items') // eager loading related data
    ->where('status', '=', 'received') // constraining the relationship
    ->get() // getting the results: Collection of Order
    ->sum('pivot.quantity'); // sum the pivot field to return a single value.

The strategy here is to find the desired Item to then get the related Order s to this Item that has a 'received' status, to finally sum the pivot attribute in order to get a single value.

It should work.

Answer 2

Considering you know the id of the item, most performant way would be to query item_order table directly. I would create a pivot model for ItemOrder and define the belongsTo(Order::class) relationship and do this:

$sum = ItemOrder::where('item_id', $someItemId)
    ->whereHas('order', function ($q) {
        return $q->where('status', 'received');
    })
    ->sum('quantity');