Link Between Purchase Order and Requisition

You have a purchase order and you have a requisition, but wait how do 
you know how this purchase order is linked with requisition. Here is the

query

SELECT prh.segment1 req_number
      ,prh.authorization_status
      ,prl.line_num req_line_num
      ,prl.item_description req_item_description
      ,prl.unit_price req_unit_price
      ,prl.quantity req_quantity
      ,pd.req_header_reference_num
      ,pd.req_line_reference_num
      ,pl.line_num
      ,pl.item_description
      ,pl.quantity
      ,pl.amount
      ,ph.segment1 po_number
      ,prd.distribution_id
      ,pd.req_distribution_id
  FROM po_requisition_headers_all prh
      ,po_requisition_lines_all   prl
      ,po_req_distributions_all   prd
      ,po_distributions_all       pd
      ,po_line_locations_all      pll
      ,po_lines_all           pl
      ,po_headers_all             ph
 WHERE prh.requisition_header_id = prl.requisition_header_id
   and prh.org_id = prl.org_id
   and prl.requisition_line_id = prd.requisition_line_id
   and prl.org_id = prd.org_id
   and prd.distribution_id = pd.req_distribution_id(+)
   and prd.org_id = pd.org_id(+)
   and pd.line_location_id = pll.line_location_id(+)
   and pd.org_id = pll.org_id(+)
   and pll.po_line_id = pl.po_line_id(+)
   and pll.org_id = pl.org_id(+)
   and pl.po_header_id = ph.po_header_id(+)
   and pl.org_id = ph.org_id(+)