Laravel Eloquent Sum of relation's column

问题

I've been working on a shoppingcart application and now I've come to the following issue..

There is a User, a Product and a Cart object.
- The Cart table only contains the following columns: "id", "user_id", "product_id" and timestamps.
- The UserModel "hasMany" Carts (because a user can store multiple products).
- The CartModel "belongsTo" a User and CartModel "hasMany" Products.

Now to calculate the total products I can just call: Auth::user()->cart()->count().

My question is: How can I get the SUM() of prices (a column of product) of the products in cart by this User?
I would like to accomplish this with Eloquent and not by using a query (mainly because I believe it is a lot cleaner).

回答1:

Auth::user()->products->sum('price');

The documentation is a little light for some of the Collection methods but all the query builder aggregates are seemingly available besides avg() that can be found at http://laravel.com/docs/queries#aggregates.

回答2:

this is not your answer but is for those come here searching solution for another problem. I wanted to get sum of a column of related table conditionally. In my database Deals has many Activities I wanted to get the sum of the "amount_total" from Activities table where activities.deal_id = deal.id and activities.status = paid so i did this.

$query->withCount([
'activity AS paid_sum' => function ($query) {
            $query->select(DB::raw("SUM(amount_total) as paidsum"))->where('status', 'paid');
        }
    ]);

it returns

"paid_sum_count" => "320.00"

in Deals attribute.

This it now the sum which i wanted to get not the count.

回答3:

I tried doing something similar, which took me a lot of time before I could figure out the collect() function. So you can have something this way:

collect($items)->sum('amount');

This will give you the sum total of all the items.

回答4:

Also using query builder

DB::table("rates")->get()->sum("rate_value")

To get summation of all rate value inside table rates.

To get summation of user products.

DB::table("users")->get()->sum("products")

来源：https://stackoverflow.com/questions/21679678/laravel-eloquent-sum-of-relations-column