problem in alv grid

Dear abapes,

I have some problem in alv grid.

I am posting my code.

DATA: BEGIN OF ITAB,

CARRID LIKE SFLIGHT-CARRID,

CONNID LIKE SFLIGHT-CONNID,

FLDATE LIKE SFLIGHT-FLDATE,

END OF ITAB.

DATA: ALV_ITAB TYPE TABLE OF ITAB,

WA_ALV_ITAB LIKE LINE OF ALV_ITAB.

SELECT * INTO CORRESPONDING FIELDS OF TABLE ALV_ITAB FROM SFLIGHT.

while selecting no datas are being fetched rather it is showing 2 columns one are showing.

one is keypart and other one is funpart.

Kindly tell me the reason.

Thanks

Ansuman