Not Sure if Laravel Distinct() is What I Should Use - laravel

Question

This might be simple but I cant seem to figure it out. Customers have many machines. I need to return just the customer name once for a list. What I'm getting is an array of all machines.
public function machine_past_due(){
$today = date('Y-m-d');
$machines_past =Machine::distinct()
->whereDate('cert_date', '<', $today)
->with('customer')
->get();
return response()->json($machines_past);
}

Answer 1

I may be misunderstanding, and I know you already have an accepted solution, but if you want customers who have machines, it seems to me answers here are coming at it from the wrong direction - you don't want machines with customers, you want customers.
As a first step:
Customers::has('machines')->get();
will give you a list of customers who have at least 1 machine.
To incorporate your date restriction, you can use whereHas() to do something like:
Customers::whereHas('machines', function (Builder $query) {
$query->whereDate('cert_date', '<', date('Y-m-d'));
})->get();
This will give you all customers who have at least one machine matching the date condition. Note it does not include the machines - just a customer list.
If you want to include a customer's machines in the results, you have to then use with(), while constraining it with the same date condition:
Customers::whereHas('machines', function (Builder $query) {
$query->whereDate('cert_date', '<', date('Y-m-d'));
})->with(['machines' => function($query) {
$query->whereDate('cert_date', '<', date('Y-m-d'));
}])->get();
This will give you a list of all customers who have at least one machine matching the date condition, and list each customers' machines as a property of the customer, accessible as $customer->machines. You can then iterate over customers and do things like (in a blade view say):
#foreach ($customers as $customer)
{{ $customer->name }}, {{ $customer->machines->count() }} machines:
#foreach ($customer->machines as $machine)
{{ $machine->cert_date }}
// ... some other $machine stuff :-)
#endforeach
#endforeach

Answer 2

Here is the solution to achieve your goal:
public function machine_past_due(){
$today = date('Y-m-d');
$machines_past =Machine::distinct()
->whereDate('cert_date', '<', $today)
->with('customer')
->get();
$machines_past = $machines_past->pluck('customer.property_name')->unique(); //added this line
return response()->json($machines_past);
}

Answer 3

force the query to only return distinct results.
This is what distinct do, here is the source code,
so when you use distinct, it will check all the columns you selected which is duplicated.
You can use groupBy instead:
$machines_past =Machine::groupBy('customer_id')
->whereDate('cert_date', '<', $today)
->with('customer')
->get();
And if you are using mysql 5.7+ and you are using strict mode in laravel, you need to disable ONLY_FULL_GROUP_BY in laravel.

Answer 4

If what you are trying to return is an array of distinct customer names from your machine collection then laravel collection have a couple of methods that can help you. Assuming your customer is a "toOne" relationship and has a name attribute then:
public function machine_past_due(){
$today = date('Y-m-d');
$machines_past = Machine::whereDate('cert_date', '<', $today)
->with('customer')
->get();
$customer_names = $machines_past
->pluck('customer.name')
->unique()
->all();
return response()->json($customer_names);
}
The code will pluck the customer name from each of the machine returned from your query and removes all duplicate before finally converting it to an array.