How to group on multiple fields including nested eager columns

Question

I have some carts, products and users. I try to get statistics like number of carts per user. And here are my models:

• user.php

   class User { public function products() { return $this->hasMany(Product::class, 'user_id'); } }

• cart.php

   class Cart { public function products() { return $this->hasMany(Product::class, 'cart_id'); } }

• product.php

   class Product { public function user() { return $this->belongsTo('User', 'user_id'); } public function cart() { return $this->belongsTo(Cart::class, 'cart_id'); } }

Here is my query:

$query = Cart::query()
        ->whereHas('products', function ($query) use ($filter) {
            $query->where('whatever', $filter);
        })
        ->join('product', 'product.cart_id', '=', 'cart.id')
        ->join('users', 'users.id', '=', 'product.user_id')
        ->groupBy('users.id')
        ->select('users.id as user_id')
        ->select('users.name')
        ->selectRaw('count(cart.id) as numberOfCarts')
        ->selectRaw('SUM(price)')
        ->orderBy('users.name')
        ->get();

What I get is number of products per user, but I want number of carts per user. when I try to group using cart.id like groupBy(['user.id', 'cart.id']) , it is worse: I get several times the same user and at each time the number of products in cart. And this total gives the same as total of number of carts get previously.

I have added jointure because I don't make it work by trying grouping on nested eager relationship. So I make it simplier.

How to fix grouping to count users carts and not their products ?

Answer 1

The issue is that count() counts the number of records returned by your MySQL query , so if you're looking at 20 rows all with the same cart.id , it's still going to count all 20 of them.

You can reduce this to what you want by only counting unique cart.id s with distinct :

$query = Cart::query()
        ->whereHas('products', function ($query) use ($filter) {
            $query->where('whatever', $filter);
        })
        ->join('product', 'product.cart_id', '=', 'cart.id')
        ->join('users', 'users.id', '=', 'product.user_id')
        ->groupBy('users.id')
        ->select('users.id as user_id')
        ->select('users.name')
        ->selectRaw('count(distinct cart.id) as numberOfCarts') // << Changed line
        ->selectRaw('SUM(price)')
        ->orderBy('users.name')
        ->get();