SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'county_id' cannot be null - laravel-8

Question

I am trying to save my data from a dynamic selected dropdown into my database but I'm having errors doing so.
This is the error I am getting.
SQLSTATE[23000]: Integrity constraint violation: 1048 Column 'county_id' cannot be null (SQL: insert into `properties` (`National_id`, `Plot_No`, `Property_Ad`, `Property_Photo`, `Property_features`, `county_id`, `sc_id`, `town_id`, `type`, `updated_at`, `created_at`) values (63636, 424545, Duplex Apartments, test.jpg, Free parking, ?, ?, ?, ?, 2023-02-18 09:42:30, 2023-02-18 09:42:30))
I need help on how to save a selected drop down to a database which is a foreign key referencing another table (county_id references id on the county table, sc_id references id on the subcounty table and town_id references id on the town table).
This is my livewire page.
<form id="add-property-form" method="POST" action="{{URL::to('saveProperty')}}">
#csrf
<div class="col-md-8">
<div class="card">
<div class="card-body">
#if ($errors->any())
<div class="alert alert-danger">
<ul>
#foreach ($errors->all() as $error)
<li class="text-white">{{ $error }}</li>
#endforeach
</ul>
</div>
#endif
<div class= "form-group">
<!--input pattern= "[a-zA-Z]{2,10}$" required-->
<p>National id</p><input type="number" required name="National_id" value="{{old('National_id')}}" class="form-control #error('National_id') is-invalid #enderror"
placeholder="Confirm your National id number">
<div class="invalid-feedback">
#error('National_id') {{$message}} #enderror
</div>
<p>Plot No</p><input type="number" required name="plot_no" value="{{old('plot_no')}}" class="form-control #error('plot_no') is-invalid #enderror"
placeholder="Please enter plot number">
<div class="invalid-feedback">
#error('plot_no') {{$message}} #enderror
</div>
<p>Property Description</p><input type="text" required name="Property_Ad" value="{{old('Property_Ad')}}" class="form-control #error('Property_Ad') is-invalid #enderror"
placeholder="Please enter property description">
<div class="invalid-feedback">
#error('Property_Ad') {{$message}} #enderror
</div>
<p>Property Features</p><input type="text" required name="Property features" value="{{old('Property_features')}}" class="form-control #error('Property_features') is-invalid #enderror"
placeholder="Please enter property features">
<div class="invalid-feedback">
#error('Property_features') {{$message}} #enderror
</div>
<p>Property Images</p><input type="file" required name="Property_Photo" value="{{old('Property_Photo')}}" class="form-control"
>
<p>Location</p>
<div class="row align-items-start">
<div class="col">
<select id="County" class="form-select-lg mb-3 form-control" wire:model = "selectedCounty" name="County">
<option value="" >County</option>
#foreach ($counties as $co)
<option value="{{$co->id}}">{{$co->name}}</option>
#endforeach
</select>
</div>
#if (!is_null($subcounty))
<div class="col">
<select id="subCounty" class="form-select-lg mb-3 form-control" wire:model = "selectedSubCounty" name="subCounty">
<option value="">SubCounty</option>
#foreach ($subcounty as $su)
<option value="{{$su->id}}">{{$su->name}}</option>
#endforeach
</select>
</div>
#endif
#if (!is_null($town))
<div class="col">
<select id="Town" class="form-select-lg mb-3 form-control" wire:model = "selectedTown" name="Town">
<option value="">Town</option>
#foreach ($town as $to)
<option value="{{$to->id}}">{{$to->name}}</option>
#endforeach
</select>
</div>
#endif
</div>
<p>Property Type</p><input type="text" required name="property_type" value="{{old('type')}}" title="2-10 characters" class="form-control #error('type') is-invalid #enderror"
placeholder="Please enter your property type">
<div class="invalid-feedback">
#error('type') {{$message}} #enderror
</div>
</div>
<input type="submit" name="submit" class="form-control btn btn-success" >
</div>
</div>
</div>
</div>
</form>
This is my view page
#extends('layout')
#section('headTitle', 'Your Properties / Add Property')
#section('pageTitle', 'Your Properties / Add Property')
#section('content')
<livewire:subcounty />
#endsection
This is my controller page.
<?php
namespace App\Http\Controllers;
use App\Models\home_owners;
use App\Models\property;
use Illuminate\Http\Request;
use Illuminate\Support\Facades\Validator;
class ProController extends Controller
{
public function viewProperties(){
$allPros = property::paginate(7);
//dd is the laravel version of var_dump() & die();
//dd($allRoles);
return view('HO.properties', ['properties'=>$allPros]);
}
public function addProperty(){
return view('HO.addproperty');
}
public function saveProperty(Request $request){
$prop = new property();
$prop->National_id=$request->National_id;
$prop->Plot_No=$request->plot_no;
$prop->Property_Ad=$request->Property_Ad;
$prop->Property_Photo=$request->Property_Photo;
$prop->Property_features=$request->Property_features;
$prop->county_id=$request->county_id;
$prop->sc_id=$request->sc_id;
$prop->town_id=$request->town_id;
$prop->type=$request->type;
if($request->hasFile('Property_photo')){
$file = $request->file('Property_photo');
$extension = $file->getClientOriginalExtension();
$filename = time().'.'.$extension;
$file->move('uploads/properties', $filename);
$prop->Property_Photo = $filename;
}
$prop->save();
return redirect('properties')->with('status',"New Property added.");
}
public function editProperty(){
}
}

Answer 1

basically it is indicating that the county_id field is being sent empty or null to the database, in your form the county_id field is called County, you need to change it:
<select id="County" class="form-select-lg mb-3 form-control" wire:model = "selectedCounty" name="County">
to
<select id="County" class="form-select-lg mb-3 form-control" wire:model = "selectedCounty" name="county_id">