Php query regarding 2 FK and 1 Primary Key - php

Question

In my table internships, I have two foreign keys id_promoter_internship and id_supervisor_internship. In the table business_contacts I have 1 primary key id_business. I'm trying to get data from the business_contacts table which is linked to the internships table. Is the following query correct?
public function update_form_business_contact($name_enterprise){
$query = "
SELECT
*
FROM business_contacts
,internships
WHERE
business_contacts.id_business = internships.id_supervisor_internship
AND internships.name_enterprise_internship = '$name_enterprise'";
$result = $this->_db->query($query);
# Go through results of teachers
if($result->rowCount()!=0){
while($row=$result->fetch()){
$contact= new businesscontact ( $row->id_business,$row->firstname_business,$row->lastname_business,$row->service_business,$row->function_business,$row->phone_business,$row->phone_secretary_business,$row->mobile_business);
}
}
return $contact;
}
My question is: Does the primary key have to reference both foreign keys? If so how would I do that.
Thanks for your help.

Answer 1

You should rewrite the query using join like:
$query = "SELECT *
FROM business_contacts bc
INNER JOIN internships i ON bc.id_business = i.id_supervisor_internship
WHERE internships.name_enterprise_internship = '$name_enterprise'";

Answer 2

If you need both ids then left join twice using both ids:
$query = "select
*
from internships i
left join business_contacts bc ON bc.id_business = i.id_supervisor_internship
left join business_contacts bc2 on bc2.id_business = i.id_promoter_internship
WHERE
i.name_enterprise_internship = '$name_enterprise'";
If you need only supervisor id:
$query = "select
*
from internships i
left join business_contacts bc ON bc.id_business = i.id_supervisor_internship
WHERE
i.name_enterprise_internship = '$name_enterprise'";
If you need only promoter id:
$query = "select
*
from internships i
left join business_contacts bc on bc.id_business = i.id_promoter_internship
WHERE
i.name_enterprise_internship = '$name_enterprise'";
To get use specific parameter in the join:
$query = "select
*
from internships i
left join business_contacts bc ON bc.id_business = i.id_promoter_internship and i.name_enterprise_internship = '$name_enterprise'";