There are two tables in the database, which are one-to-many relationships:

Main table (reservation information): dbo.Reservation

    [ReservationID] [INT] IDENTITY(1,1) NOT NULL,
    [ReservationNo] [NVARCHAR](24) NOT NULL,
    ......

Details table (reservation details): dbo.ReservationDetail

    [ReservationDetailID] [INT] IDENTITY(1,1) NOT NULL,
    [ReservationID] [INT] NOT NULL,                          --外键
    ......

The code of Model is as follows:

Reservation.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class Reservation extends Model
{
    protected  $table = 'dbo.Reservation';

    public function hasManyReservationDetails()
    {
        return $this->hasMany('App\Models\ReservationDetail', 'ReservationID', 'ReservationID');
    }
}

ReservationDetail.php

<?php

namespace App\Models;

use Illuminate\Database\Eloquent\Model;

class ReservationDetail extends Model
{
    protected  $table = 'dbo.ReservationDetail';

    public function belongsToReservation()
    {
        return $this->belongsTo('App\Models\Reservation', 'ReservationID', 'ReservationDetailID');
    }

}

Call in an API controller

<?php

namespace App\Api\Controllers;

use App\Models\Reservation;
use App\Models\ReservationDetail;
use App\Http\Requests;

class ReservationController extends BaseController
{

    public function showByReservationNo($reservation_no)
    {

        $reservation_details = ReservationDetail::all()
            ->belongsToReservation()
            ->where('ReservationNo', '=', $reservation_no)
            ->get();

        return $reservation_details;
    }
}

The error message returned by Laravel is as follows:

  "message": "Method belongsToReservation does not exist.",
  "status_code": 500,

What is the reason for this? Is it a namespace problem?

What I hope to achieve is to use a certain conditional association of the main table to query the detailed table and return the data of the detailed table. The query SQL statement is as follows:

SELECT ReservationDetail.*
FROM ReservationDetail
INNER JOIN Reservation ON Reservation.ReservationID = ReservationDetail.ReservationID
WHERE Reservation.ReservationNo = 'xxx'

May I ask you all, what is the problem? How should I write the correct grammar?

Another question is if you want the data returned to be returned by merging the main table and the detailed table into one object, for example:

{
  "ReservationID": "1", 
  "ReservationNo": "201601011000", 
  "ReservationDetails": [
    {
      "ReservationDetailID": "1", 
    }, 
    {
      "ReservationDetailID": "2", 
    }
  ]
}

How to write related query? Please give me some advice, thank you very much! ! !