create table t1 ( id integer, para text, valu integer );

insert into t1 values (  1 , 'a',  100  );
insert into t1 values (  1 , 'b',  100  );
insert into t1 values (  1 , 'a',  100  );
insert into t1 values (  1 , 'b',  200  );
insert into t1 values (  1 , 'a',  100  );
insert into t1 values (  1 , 'c',  200  );
insert into t1 values (  2 , 'a',  100  );
insert into t1 values (  2 , 'a',  100  );
insert into t1 values (  2 , 'b',  200  );
insert into t1 values (  2 , 'a',  100  );
insert into t1 values (  3 , 'b',  100  );
insert into t1 values (  3 , 'b',  200  );
insert into t1 values (  3 , 'c',  200  );

select id, para, sum(valu) from t1 group by id, para;

--

create function td(char,char) returns char as '
  select $1 || \'    <td>\' || $2 || \'</td>\\n\'
' language SQL;
create aggregate td( sfunc = td, basetype = char, stype = char, initcond = '' );

create function tb(char,char) returns char as '
  select $1 || \'  <tr>\\n\' || $2 || \'  </tr>\\n\'
' language SQL;
create aggregate tb( sfunc = tb, basetype = char, stype = char, initcond = '' );

select '<table>\n'||tb(td('',coalesce(id::text,' '))||valu)||'</table>\n' as html from (
  select  20  as ordr, id, td(valu::text) as valu from (
    select id, para, coalesce(sum(valu), 0 ) as valu from t1
    natural right join (
      select id, para from ( select distinct para from t1 ) as c
      cross join ( select distinct id from t1 ) as d
    ) as b group by id, para order by id, para
  ) as a group by id
  union select  10  as ordr, null as id, td(para::text) as valu from (
    select distinct para from t1 order by para
  ) as e order by ordr, id
) as f;

--

drop aggregate tb(char);
drop function tb(char,char);
drop aggregate td(char);
drop function td(char,char);
drop table t1;