How to set the field can be null when there is relationship - php

Question

I have an issue, when I delete a contractor that relate to that one residence, there will be an error something like trying to get property name in this line in index view <li>Contractor: {{$res->contractor->name}}. I want to make it possible by deleting the contractor, then the contractor field in residence view could be empty or null. And this can be vice versa. How can I do that? Here is my model.
Residential.php
class Residential extends Model
{
protected $fillable = ['name','res_code','postcode','city','state','image','contractor_id'];
public function contractor()
{
return $this->belongsTo(Contractor::class);
}
public function buyer()
{
return $this->hasMany(Buyer::class);
}
}
Contractor.php
class Contractor extends Model
{
protected $table = 'contractors';
protected $fillable = ['name','address','phone_no','email','avatar'];
public function residential()
{
return $this->hasMany(Residential::class);
}
public function users()
{
return $this->morphMany(User::class, 'typable');
}
}
Here is my controller.
ResidentialController.php
class ResidentialController extends Controller
{
public function index(Request $request)
{
$contractor = Contractor::find($request->id);
$residential = Residential::all();
return view('residentials.index',compact('residential','contractor'));
}
ContractorController.php
public function index(Request $request)
{
$residential = Residential::find($request->id);
$contractor = Contractor::all();
return view('admins.contractors.index', compact('residential', 'contractor'));
}
And here is my view.
residentials\index.blade.php
#foreach($residential as $res)
<div class="panel-body">
<ul class="list-unstyled list-justify">
<li>ID: {{$res->id}}</li>
<li>Code: {{$res->res_code}}</li>
<li>Postcode: {{$res->postcode}}</li>
<li>City: {{$res->city}}</li>
<li>State: {{$res->state}}</li>
<li>Contractor: {{$res->contractor->name}}
</ul>
</div>
#endforeach
contractors\index.blade.php
<table class="table table-hover" id="contractor-table">
<tr>
<th>ID</th>
<th>Company</th>
<th>Phone No</th>
<th>Email</th>
<th>Residence</th>
<th>Action</th>
</tr>
#foreach($contractor as $cont)
<tr class="contractor{{$cont->id}}">
<td>{{$cont->id}}</td>
<td>{{$cont->name}}</td>
<td>{{$cont->phone_no}}</td>
<td>{{$cont->email}}</td>
<td>{{$cont->residential->pluck('name')->implode(', ')}}</td>
#endforeach
</table>
I hope there is someone can understand my problem and can help me.

Answer 1

You have to use LEFT JOIN in your query.Using of it you will automatic receive NULL value.
The SQL LEFT JOIN returns all rows from the left table, even if there are no matches in the right table. This means that if the ON clause matches 0 (zero) records in the right table; the join will still return a row in the result, but with NULL in each column from the right table.
This means that a left join returns all the values from the left table, plus matched values from the right table or NULL in case of no matching join predicate.
Reference link : https://www.tutorialspoint.com/sql/sql-left-joins.htm#:~:text=Advertisements,column%20from%20the%20right%20table.