Bagaimana cara mengatasi ORA-00937:bukan fungsi grup grup tunggal saat menghitung persentase?

Analytics adalah teman Anda:

SELECT DISTINCT
       areas
      ,COUNT(currentitems.itemid)
       OVER (PARTITION BY areas) * 100
       / COUNT(*) OVER () Percentage
FROM allitems, currentitems
WHERE allitems.itemid = currentitems.itemid(+);