Hi Shelwin Wei,
Befor using the FOR ALL Entries IN LT_NVBELN yoou have to apply condition whether LT_NVBELN is initial or not like this
IF NOT LT_NVBELN[] is initial.
endif.
if you haven't done this then the system will fetch all netries from table LTAK.
Also as to answer you question the second query will also fetch the entire data form that table.
Thanks & Regard.
Priyesh Shah.