Hi,
You can use IS INITIAL and IS NOT INITIAL for checking if the 2 tables are empty or not and perform 2 select queries as mentioned above.
for e.g.
SELECT * FROM BKPF INTO TABLE IT_BKPF1 WHERE BUDAT EQ '20141016' AND BUDAT GE '20140101'.
SELECT * FROM BKPF INTO TABLE IT_BKPF2 WHERE BUDAT LE '20141130'.
SELECT * FROM BKPF INTO TABLE IT_BKPF2 WHERE BUDAT LE '20141016'.
IF IT_BKPF1 IS NOT INITIAL AND IT_BKPF2 IS NOT INITIAL.
FLAG = 'TRUE'.
ENDIF.
IF IT_BKPF1 IS NOT INITIAL AND IT_BKPF3 IS NOT INITIAL.
FLAG = 'FALSE'.
ENDIF.