Hi Vinay,
I am afraid you don't have option like FOR ALL ENTRIES in Oracle native sql.
You can make use of field-symbols for faster internal table processing.
Once you have both SAP table data and External DB table data in separate internal tables, sort them. Then compare the data by making use of read statement with BINARY SEARCH for faster comparison.
The above process will be very best.
For instance,
sort : isap_ztable,iora_ztable.
loop at isap_ztable ASSIGNING <fs_sap>.
read table iora_ztable ASSIGNING <fs_ora> with key zfield = <fs_sap>-zfield BINARY SEARCH.
if sy-subrc = 0.
if <fs_ora> NE <fs_sap>.
"DATA DIFFERS
endif
endif.
endloop.
Regards.