Oracle 11g Release 2

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create table tabla(e number, monto number);
insert into tabla (e, monto)
SELECT 1, 10 FROM DUAL UNION 
SELECT 2, 20 FROM DUAL UNION 
SELECT 1, 30 FROM DUAL UNION 
SELECT 2, 40 FROM DUAL;
4 rows affected

select e, 
       sum(monto),
       sum(sum(monto)) over ()
       from tabla
       group by e;
       


E
SUM(MONTO)
SUM(SUM(MONTO))OVER()


1
40
100

2
60
100