Query to get all Purchase Requisition without a Purchase Order in Oracle APPS

SELECT prh.segment1 requisition_number,

         TO_CHAR(prh.creation_date, 'DD-MON-RRRR') created_on,

         TO_CHAR(prl.creation_date, 'DD-MON-RRRR') line_creation_date,

         prl.line_num,

         msi.segment1 item_code,

         prl.item_description description,

         prl.quantity ,

         TO_CHAR(prl.need_by_date, 'DD-MON-RRRR') required_date,

         requestor.full_name requestor_name,

         buyers.agent_name buyer_name

    FROM po.po_requisition_headers_all prh,

         po.po_requisition_lines_all prl,

         apps.per_people_f requestor,

         (SELECT DISTINCT agent_id, agent_name 

    FROM apps.po_agents_v) buyers,

         po.po_req_distributions_all prd,

         inv.mtl_system_items_b msi,

         po.po_line_locations_all pll,

         po.po_lines_all pl,

         po.po_headers_all ph

   WHERE     prh.requisition_header_id = prl.requisition_header_id

         AND prl.requisition_line_id = prd.requisition_line_id

         AND requestor.person_id = prh.preparer_id

         AND prh.creation_date BETWEEN requestor.effective_start_date

                                   AND requestor.effective_end_date

         AND buyers.agent_id(+) = msi.buyer_id

         AND msi.inventory_item_id = prl.item_id

         AND msi.organization_id = prl.destination_organization_id

         AND pll.line_location_id(+) = prl.line_location_id

         AND pll.po_header_id = ph.po_header_id(+)

         AND pll.po_line_id = pl.po_line_id(+)

         AND prh.authorization_status = 'APPROVED'

         AND pll.line_location_id IS NULL

         AND prl.closed_code IS NULL

         AND NVL (prl.cancel_flag, 'N') <> 'Y'

         AND prh.org_id = 123456

ORDER BY 1, 2