Hi! I've got problem with sql statement..

in dataset like
col1 col2
a 1
b 3
c 5
d null
e 2

i must to sum col2, but if 1 single value of this column is null then sum
must result to null, according this i wrote statement:

select sum(col2) from table1

but this query results with 11.

any idea??!!

create table table1 (col1 char(1), col2 number);



insert into table1 values('a',1);

insert into table1 values('b',3);

insert into table1 values('c',5);

insert into table1 values('d',null);

insert into table1 values('e',2);



commit;



select sum(col2) from table1;