如何在Laravel 5.7中将数据输入限制为数据库

Question

How could I limit the data that I am writing to the database.

I am trying to map Bank details to Districts. I would like to limit the entry of Bank details to 1 District.

To be precise, user should only be able to create a bank name for a district. When they try to create a new record they would be treated with error stating that only One record should be created.

Database Tables:

District 
| id 
| district_name

Bank
| id 
| bank_name
| district_id

I have thought of showing the data of the districts that not in the bank table to a select menu.

How would I limit that in eloquent relationship or are there any other options,

Another option is to limit the result to the latest creates bank Id. But I dont think this is a good idea to consider.

What I tried,

Bank Controller,

use Bank;

 public function create()
    {
        $districts = Districts::all();
        $banks = Bank::all();
        foreach($banks->districts as $bank)
        $banks1 = $bank->district_name;
        return($bank1);

        // return view('bank-create',compact('districts'));
    }

The above code is not working, I just tried and I was not able to get through it.

I was expecting the result of the query to pass in to below select,

 <select name="district_option1" class="form-control  ml-5" id="">
                        @foreach ($bank1 as $banks1)
                        <option value="{{$banks1->id}}">{{$banks1->district_name}} </option>
                        @endforeach
                    </select> 

My Model:

Bank

public function districts(){
    return $this->belongsTo('App\Districts','district_id','id');
}

District :

 public function bank(){
     return $this->hasOne('App\Bank','id','district_id'); }

Answer 1

You may use unique validation for this purpose.

    public function create(Request $request)
    {
        $request->validate([
           'district_id' => 'reuqired|unique:banks,district_id'
        ]);
     }

Here you are checking if there are any records for this district.