I have a ztable used in a program wherin I have a doubt of performance issue in selection.Its like :
SELECT ship_no invoice_no
INTO TABLE it_ship_no_hist
FOR ALL ENTRIES IN it_freight
WHERE ship_no = it_freight-tknum.
there are 7 key fields in this table out of which one ( tknum ) is used in a where condition.The table is without any index.
For performance purpose should I create an index with the very field 'tknum' in the index..can I do that or index should be created only along with non key fields.