thank you AMIT
i found the solution like this
TABLES ZDB2.
DATA wa_db TYPE ZDB2 .
DATA itab TYPE STANDARD TABLE OF zdb2.
data flag type i .
SELECT COUNT(*) INTO flag FROM zdb2.
wa_db-ID = flag+1.
wa_DB-DATED = sy-datum.
wa_DB-chekin = sy-uzeit.
wa_DB-useru = sy-uname.
insert zdb2 FROM wa_db .
IF sy-subrc = 0.
MESSAGE wa_DB-ID TYPE 'I' .
else.
MESSAGE 'Error' TYPE 'I' .
ENDIF.