EWBEZ need to bring Sq01

HI ,

I Have done below coding to get EWBEZ get in additional field i have defined.

data :mara-EXTWG like mara-EXTWG.
Clear : EXT_MATERIALGROUPTEXT.
SELECT single EWBEZ
into EXT_MATERIALGROUPTEXT
from TWEWT
where EXTWG = mara-EXTWG
and SPRAS = sy-langu.

But when I run query field is Blank .

Please help me .

Many Thnaks