Relationship with same table

To create a self-referential relationship in Eloquent, you can use a "many-to-many" relationship with a pivot table. This is useful when you want to associate a contract with other contracts. Here's how you can set it up:

1. Create a Pivot Table:

   First, create a migration for the pivot table. This table will store the associations between contracts.

   php artisan make:migration create_contract_contract_table --create=contract_contract
   

   In the migration file, define the table structure:

   Schema::create('contract_contract', function (Blueprint $table) {
       $table->id();
       $table->foreignId('contract_id')->constrained('contracts')->onDelete('cascade');
       $table->foreignId('related_contract_id')->constrained('contracts')->onDelete('cascade');
       $table->timestamps();
   });
   

   Run the migration:

   php artisan migrate
   

2. Define the Relationship in the Model:

   In your Contract model, define a many-to-many relationship to itself:

   use Illuminate\Database\Eloquent\Model;
   
   class Contract extends Model
   {
       public function relatedContracts()
       {
           return $this->belongsToMany(Contract::class, 'contract_contract', 'contract_id', 'related_contract_id');
       }
   }
   

   This method relatedContracts will allow you to access all contracts related to a given contract.

3. Using the Relationship:

   You can now use this relationship to associate contracts with each other:

   // Assuming you have two contract instances
   $contract1 = Contract::find(1);
   $contract2 = Contract::find(2);
   
   // Attach a related contract
   $contract1->relatedContracts()->attach($contract2->id);
   
   // Retrieve related contracts
   $relatedContracts = $contract1->relatedContracts;
   

This setup allows you to associate contracts with each other using a pivot table, similar to a many-to-many relationship. You can attach, detach, and sync related contracts as needed.