Parece que você quer o total em execução. Você pode usar o
SUM analítico função para isso. select mnth,
sum(stmts) over (order by mnth) stmts
from (select TRUNC(ACTHX.STMT_HX_STMT_DATE, 'MM') AS MNTH,
COUNT(ACTHX.INVOICE) as STMTS
from ACTHX
group by TRUNC(ACTHX.STMT_HX_STMT_DATE, 'MM'))
ORDER BY mnth
