delete POs with missing edocs

DELETE
FROM
pur_po_t
WHERE
FDOC_NBR IN
(
  SELECT
  po.FDOC_NBR
  FROM
  pur_po_t po
  left join
  krew_doc_hdr_t hdr ON
  hdr.doc_hdr_id=po.FDOC_NBR
  WHERE
  hdr.doc_hdr_id IS NULL
)