Select `order`.orderid, clients.company_name AS client, `order`.issue_date AS issued_date, `order`.seq_number AS doc_number, document_type.heading
From
`order`
Inner Join clients ON `order`.clientsid = clients.clientsid
Inner Join documents ON `order`.documentsid = documents.documentsid
Inner Join document_type ON document_type.document_typeid = documents.document_typeid