ABAP 取数问题

[liuping234232783]

FORM get_data.
select vbeln from vbak
into CORRESPONDING FIELDS OF TABLE it_header.

LOOP AT it_header INTO wa_header.
select singer vbap~posnr
from vbap
where vbeln = wa_header-vbeln.
modify it_header FROM wa_header.
ENDLOOP.
ENDFORM.


现在是VBAK的一行数据可能会对VBAP的多行数据，LOOP现在用SINGER只会读取一行，怎么样在LOOP写代码取出VBAK对应VBAP的多行数据。谢谢