Is SQL GROUP BY a design flaw? [closed]

Answer 1

The "superflous" attributes influence the ordering of the result.

Consider:

create table gb (
  a number,
  b varchar(3),
  c varchar(3)
);

insert into gb values (   3, 'foo', 'foo');
insert into gb values (   1, 'foo', 'foo');
insert into gb values (   0, 'foo', 'foo');

insert into gb values (  20, 'foo', 'bar');
insert into gb values (  11, 'foo', 'bar');
insert into gb values (  13, 'foo', 'bar');

insert into gb values ( 170, 'bar', 'foo');
insert into gb values ( 144, 'bar', 'foo');
insert into gb values ( 130, 'bar', 'foo');

insert into gb values (2002, 'bar', 'bar');
insert into gb values (1111, 'bar', 'bar');
insert into gb values (1331, 'bar', 'bar');

This statement

select sum(a), b, c
  from gb
group by b, c;

results in

    44 foo bar
   444 bar foo
     4 foo foo
  4444 bar bar

while this one

select sum(a), b, c
  from gb
group by c, b;

results in

   444 bar foo
    44 foo bar
     4 foo foo
  4444 bar bar