For all entries in select request

Hello Masters,

     I am actually learning abap and i am having some trouble with the for all entries in select requests. I am trying to get the item description (arktx) from the table vbap into a structure for all entries in a table. So i am trying to do this request :

select arktx

      from vbap

      into LT_SFC_POCOT_SHOWM-arktx             " type vbap-arktx

      for all entries in sfc_pocot[]                            " table (i guess)

      where vbeln = sfc_pocot-kdauf and

            posnr = sfc_pocot-kdpos.

     endselect.

but unfortunately, my structure stays empty.

Any idea or tips?

Thanks in advance!
Max