Tabella incrociata con un numero elevato o indefinito di categorie

create table vote (Photo integer, Voter text, Decision text);
insert into vote values
(1, 'Alex', 'Cat'),
(1, 'Bob', 'Dog'),
(1, 'Carol', 'Cat'),
(1, 'Dave', 'Cat'),
(1, 'Ed', 'Cat'),
(2, 'Alex', 'Cat'),
(2, 'Bob', 'Dog'),
(2, 'Carol', 'Cat'),
(2, 'Dave', 'Cat'),
(2, 'Ed', 'Dog'),
(3, 'Alex', 'Horse'),
(3, 'Bob', 'Horse'),
(3, 'Carol', 'Dog'),
(3, 'Dave', 'Horse'),
(3, 'Ed', 'Horse'),
(4, 'Alex', 'Horse'),
(4, 'Bob', 'Horse'),
(4, 'Carol', 'Cat'),
(4, 'Dave', 'Horse'),
(4, 'Ed', 'Horse'),
(5, 'Alex', 'Dog'),
(5, 'Bob', 'Cat'),
(5, 'Carol', 'Cat'),
(5, 'Dave', 'Cat'),
(5, 'Ed', 'Cat')
;

La domanda per il gatto:

select photo,
    alex + bob + carol + dave + ed as Total,
    alex, bob, carol, dave, ed
from crosstab($$
    select
        photo, voter,
        case decision when 'Cat' then 1 else 0 end
    from vote
    order by photo
    $$,'
    select distinct voter
    from vote
    order by voter
    '
) as (
    photo integer,
    Alex integer,
    Bob integer,
    Carol integer,
    Dave integer,
    Ed integer
);
 photo | total | alex | bob | carol | dave | ed 
-------+-------+------+-----+-------+------+----
     1 |     4 |    1 |   0 |     1 |    1 |  1
     2 |     3 |    1 |   0 |     1 |    1 |  0
     3 |     0 |    0 |   0 |     0 |    0 |  0
     4 |     1 |    0 |   0 |     1 |    0 |  0
     5 |     4 |    0 |   1 |     1 |    1 |  1

Se il numero di elettori è grande o non noto, è possibile farlo in modo dinamico:

do $do$
declare
voter_list text;
r record;
begin

drop table if exists pivot;

voter_list := (
    select string_agg(distinct voter, ' ' order by voter) from vote
    );

execute(format('
    create table pivot (
        decision text,
        photo integer,
        Total integer,
        %1$s
    )', (replace(voter_list, ' ', ' integer, ') || ' integer')
));

for r in
select distinct decision from vote
loop
    execute (format($f$
        insert into pivot
        select
            %3$L as decision,
            photo,
            %1$s as Total,
            %2$s
        from crosstab($ct$
            select
                photo, voter,
                case decision when %3$L then 1 else 0 end
            from vote
            order by photo
            $ct$,$ct$
            select distinct voter
            from vote
            order by voter
            $ct$
        ) as (
            photo integer,
            %4$s
        );$f$,
        replace(voter_list, ' ', ' + '),
        replace(voter_list, ' ', ', '),
        r.decision,
        replace(voter_list, ' ', ' integer, ') || ' integer'
    ));
end loop;
end; $do$;

Il codice sopra ha creato il pivot della tabella con tutte le decisioni:

select * from pivot where decision = 'Cat';