具有两列的同一个表上的多个关系 Laravel

Question

If the bookstore does not have any books in stock, this bookstore can purchase books from the other bookstore it is contracted with.

book_transfers table is as follows.

ID | sender_bookstore_id | delivery_bookstore_id 
1  | 2                   | 3  
2  | 1                   | 2  
3  | 3                   | 1

books table

ID | store_name  
1  | London Garden Book Store
2  | Englaland Cafe Book
3  | Domesday Book Store           

Two-column sender_bookstore_id and delivery_bookstore_id belong to the same table. The name of this table books.

My Controller code is below:

$data = BookTransfer::join('books', 'books.id', '=', 'book_transfers.sender_bookstore_id')
         ->select(
             'book_transfers.*',
             'book_transfers.sender_bookstore_id as sender_id',
             'book_transfers.delivery_bookstore_id as delivery_id',
             'books.store_name as sender_store_name'
         )
         ->groupBy('book_transfers.id')
         ->get();
         return $data;

I can only get sender_store_name here. I need to add extra code for delivery_store_name in the above controller But I don't know how to get delivery_store_name .

Best Regards,

Answer 1

Using relation would be much more simpler.

// BookTransfer Model
public function sender(){
     return $this->belongsTo(Book::class, 'sender_bookstore_id');
}

public function delivery(){
     return $this->belongsTo(Book::class, 'delivery_bookstore_id ');
}

Your controller would look like this

$data = BookTransfer::with(['sender', 'delivery'])->get();

Answer 2

If you want to get the datas by join , you can join the same books table again, and alias it another name:

BookTransfer::join('books AS sender_books', 'sender_books.id', '=', 'book_transfers.sender_bookstore_id')
            ->join('books AS delivery_books', 'deliery_books.id', '=', 'book_transfers.delivery_bookstore_id')
            ->select(
                 'book_transfers.*',
                 'book_transfers.sender_bookstore_id AS sender_id',
                 'book_transfers.delivery_bookstore_id AS delivery_id',
                 'sender_books.store_name AS sender_store_name',
                 'delivery_books.store_name AS delivery_store_name'
             )