PO’S Which Does Not Have Any PR’S

SELECT
,prh.segment1 "PR NUM"
,trunc(prh.creation_date) "CREATED ON"
,trunc(prl.creation_date) "Line Creation Date"
,prl.line_num "Seq #"
,msi.segment1 "Item Num"
,prl.item_description "Description"
,prl.quantity "Qty"
,trunc(prl.need_by_date) "Required By"
,ppf1.full_name "REQUESTOR"
,ppf2.agent_name "BUYER"
FROM
,po.po_requisition_headers_all prh
,po.po_requisition_lines_all prl
,apps.per_people_f ppf1
,(select distinct agent_id,agent_name from apps.po_agents_v ) ppf2
,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
ppf1.person_id = prh.preparer_id and
prh.creation_date between ppf1.effective_start_date and ppf1.effective_end_date and
ppf2.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'
ORDER BY 1,2