The following is Informix behavior:

informix@zeus:/usr/informix72> dbaccess - -
> create database nulltest in datadbs;
Database created.

> create table t1 (a int4, b char(2), c char(2));
  201: A syntax error has occurred.
Error in line 1
Near character position 20

> create table t1 (a int, b char(2), c char(2));
Table created.

> insert into t1 (a,c) values (1,'x');
1 row(s) inserted.
> insert into t1 (a,c) values (2,'x');
1 row(s) inserted.
> insert into t1 (a,c) values (3,'z');
1 row(s) inserted.
> insert into t1 (a,c) values (2,'x');
1 row(s) inserted.
> select * from t1;
          a b  c
          1    x
          2    x
          3    z
          2    x

4 row(s) retrieved.
> select b,c,sum(a) from t1 group by b,c;
b  c             (sum)

   x                 5
   z                 3

2 row(s) retrieved.
> select b,c,sum(a) from t1 group by b,c order by c;
b  c             (sum)

   x                 5
   z                 3

2 row(s) retrieved.
>


Andreas

Mon, 26 Jan 1998 12:39:07 +0100
Zeugswetter Andreas DBT <Andreas.Zeugswetter@telecom.at>
Re: [HACKERS] Group By, NULL values and inconsistent behaviour.