SELECT
contact_person.contact_personid,
contact_person.lastname as 'contact_person.lastname',
contact_person.firstname as 'contact_person.firstname',
clients.company_name as 'clients.company_name',
client_branch.branch_name as 'client_branch.branch_name',
contact_person.employee_number as 'contact_person.employee_number',
contact_person.email_address as 'contact_person.email_address'
FROM
contact_person
Left Join client_branch ON client_branch.client_branchid = contact_person.client_branchid
Left Join clients ON clients.clientsid = contact_person.clientsid