Convert Laravel query to Eager Loading - php

Question

I've been leaning Laravel and trying to implement something and I did, it worked but I heard that it might be possible to do the same in an easier way using Eager Loading.
Imagine that we have 4 tables: garages, cars, securities, places.
garages is where you can find the cars, securities is the security that is keeping that car safe inside of a garage, and places is where you can find garages similar to that one.
What I want is to list garages and join the three tables that is cars, securities and places like this:
Garage 1 has 2 cars with 3 securities and has 3 more garages similar
Garage 2 has 1 cars with 1 securities and has 2 more garages similar
And here is the query:
select
g.garage_name,
count(distinct c.car_id) as count_cars,
count(distinct s.security_id) as count_securities,
count(distinct p.place_id) as count_places
from garages g
left join cars c on c.garage_id = g.garage_id
left join securities s on s.car_id = c.car_id
left join places p on p.garage_id = g.garage_id
group by g.garage_name
order by g.garage_name;
It's working, as you can see here.
I converted it to:
$garages = Garages::select('garage_name',
DB::raw('count(distinct cars.car_id) as count_cars'),
DB::raw('count(distinct securities.security_id) as count_securities'),
DB::raw('count(distinct places.place_id) as count_places'))
->leftJoin('cars', 'cars.garage_id', '=', 'garages.garage_id')
->leftJoin('securities', 'securities.car_id', '=', 'cars.car_id')
->leftJoin('places', 'places.garage_id', '=', 'garages.garage.id')
->groupBy('garages.garage_name')
->orderBy('garages.garage_name')
->get();
As I said above, it's working but I'm wondering if there's an easier way for doing this using Eager Loading and how to convert?
When I say easier I mean more readable, separated, the right way instead of that big query.

Answer 1

Lets say you do have the 4 Eloquent Model classes for the entities.
If that's the case, you can try eager loading through the Eloquent ORM.
$Garages = Garage::with(['cars','places', 'securities'])->get();
Then you may prepare the necessary output as you like using the returned result set which is a collection (Illuminate\Support\Collection). You can transform the items in a collection as any way you like. Here is an example.
In your case, I am assuming this would be the way to do it.
$Garages->transform(function($garage) {
return array(
'garage_name' => $garage->garage_name,
'count_cars' => $garage->cars->count(),
'count_securities' => $garage->securities->count(),
'count_places' => $garage->places->count(),
// add as many custom details you want here
);
});
return $Garages->toArray(); // see the output
Now I hope you got the idea.
Keep in mind that your model class files should have the relationships. It should be like the following.
class Garage extends Eloquent {
public function cars() {
return $this->hasMany('Car');
}
public function securities()
{
return $this->hasMany('Security');
}
public function places()
{
return $this->hasMany('Place');
}
}
class Car extends Eloquent {
// relationships here
}
class Security extends Eloquent {
// relationships here
}
class Place extends Eloquent {
// relationships here
}
This is just a simple example to help you understand.
Enjoy ! :D