create table t1(id number primary key,name varchar2(100));
insert into t1 values(1,'aaa');
insert into t1 values(2,''bbb');
commit;
create or replace function fun1(p_id number ) return varchar2 is
Result varchar2(100 );
begin
select name||'aa' into Result from t1 where id=p_id;
return( Result);
end fun1;
update t1 set name=(fun1( 2)) where 1= 1;