cursor 函数可以使表中嵌套另外一个表。
select pha.po_header_id, pha.segment1, cursor(select pla.line_num, pla.unit_price from po_lines_all pla where pha.po_header_id=pla.po_header_id),
cursor(select plla.shipment_num, plla.quantity_received from po_line_locations_all plla where pha.po_header_id=plla.po_header_id),
cursor(select segment1 from po_headers_all phaa where phaa.po_header_id=pha.po_header_id)
from po_headers_all pha
