Found the below SQL in a code. Isn't the outer NVL unnecessary?
select nvl(sum(nvl(order_value_n,0)), 0)
into v_ord_value
from order_dtl
where year_code_c = iv_year_code
and order_id_c = iv_ord_id
and po_element_c = iv_po_code;
exception when no_data_found then v_ord_value := 0;