How to Query if Multiple Columns Reference to the Same Table - sql

Question

I am facing an issue here. I have a table called application and it will record who requests the application, who approves it, and who rejects it. The issue is the Requestor_id, Approver_id and Rejector_id are references to the same table. How can I query for the requestor_name, approver_name, and rejector_name in Laravel
Application table
Requestor_id ( reference to user id)
Application_Status
Module_id
Approver_id ( reference to user id)
Rejector_id ( reference to user id)
created_at
updated_at
Below is what I have tried but it can only retrieve for the requestor name
$Approval_Logs = DB::table('application')
->select('application.id','application.Application_Status', 'users.name','application.Approver_id','application.Rejector_id', 'ems_application.Request_Category','application.updated_at')
->join('ems_application', 'ems_application.Application_id', '=', 'application.id')
->join('users', 'users.id', '=', 'application.requestor_id')
->whereIn('application.Application_Status',['approved','rejected'])
->get()
->toArray();
I hope I can receive some hints from you. Thanks in advance!

Answer 1

You may use aliases in your joins also.
$Approval_Logs = DB::table('application')
->select(
'application.id',
'application.Application_Status',
'application.Approver_id',
'approver.name as approver_name',
'application.requestor_id',
'requestor.name as requestor_name',
'application.Rejector_id',
'rejector.name as rejector_name',
'ems_application.Request_Category',
'application.updated_at'
)
->join('ems_application', 'ems_application.Application_id', '=', 'application.id')
->join('users as requestor', 'requestor.id', '=', 'application.requestor_id')
->join('users as approver', 'approver.id', '=', 'application.approver_id')
->join('users as rejector', 'rejector.id', '=', 'application.rejector_id')
->whereIn('application.Application_Status',['approved','rejected'])
->get()
->toArray();
I am not completely familiar with your application, however you may want to utilize left_join instead of join for the approver and rejector joins in the event that there was not an approver or rejector.

Answer 2

If you would like to do it the "Laravel" way. I would create a model called Application and create relations
class Application extends Model {
public function requestor(){
return $this->belongsTo(Users::class, 'requestor_id');
}
public function approver(){
return $this->belongsTo(Users::class, 'approver_id');
}
public function rejector(){
return $this->belongsTo(Users::class, 'rejector_id');
}
}
Then in your controller, you can run the following query:
$application = Application::whereHas('requestor', function($query) {
$query->where('first_name', 'John');
})->whereHas('approver', function($query) {
$query->where('first_name', 'Peter');
})->whereHas('rejector', function($query) {
$query->where('first_name', 'Michael');
})->get();
That should query the users table for the first names. I don't know how efficient this will be, but give it a try;