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')
;
猫のクエリ:
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
有権者の数が多いか不明な場合は、動的に行うことができます。
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; $do$;
上記のコードは、すべての決定を含むテーブルピボットを作成しました:
select * from pivot where decision = 'Cat';