Hmmm. Pokud interpretuji „poslední čtyři čtvrtletí“ jako „poslední čtyři čtvrtletí, která jsou v datech“, pak je zde jedna metoda.
Za prvé, můžete získat čtyři čtvrtiny takto:
select distinct p_year, p_quarter
from production p
order by p_year desc, p_quarter desc
limit 4;
Můžete je vyčíslit pomocí proměnných:
select p_year, p_quarter, (@rn := @rn + 1) as enum
from (select distinct p_year, p_quarter
from production p
order by p_year desc, p_quarter desc
limit 4
) p cross join
(select @rn := 0) params
Potom to můžete použít v dotazu k pivotování dat:
select p.person_id,
sum(case when seqnum = 1 then num else 0 end) as num_quarter_1,
sum(case when seqnum = 2 then num else 0 end) as num_quarter_2,
sum(case when seqnum = 3 then num else 0 end) as num_quarter_3,
sum(case when seqnum = 4 then num else 0 end) as num_quarter_4
from production p join
(select p_year, p_quarter, (@rn := @rn + 1) as seqnum
from (select distinct p_year, p_quarter
from production p
order by p_year desc, p_quarter desc
limit 4
) p cross join
(select @rn := 0) params
) yq
using (p_year, p_quarter)
group by p.person_id;
EDIT:
Pokud definujete čtvrtletí na základě aktuálního čtvrtletí, můžete udělat něco docela podobného:
select p.person_id,
sum(case when seqnum = 1 then num else 0 end) as num_quarter_1,
sum(case when seqnum = 2 then num else 0 end) as num_quarter_2,
sum(case when seqnum = 3 then num else 0 end) as num_quarter_3,
sum(case when seqnum = 4 then num else 0 end) as num_quarter_4
from production p join
(select year(curdate()) as p_year, quarter(curdate()) as p_quarter, 1 as seqnum union all
select year(curdate() - interval 1 quarter) as p_year, month(curdate() - interval 1 quarter) as p_quarter, 2 as seqnum union all
select year(curdate() - interval 2 quarter) as p_year, month(curdate() - interval 2 quarter) as p_quarter, 3 as seqnum union all
select year(curdate() - interval 2 quarter) as p_year, month(curdate() - interval 3 quarter) as p_quarter, 4 as seqnum
) yq
using (p_year, p_quarter)
group by p.person_id;
Existují i jiné přístupy, například:
select person_id,
sum(case when year(curdate()) = p_year and quarter(curdate()) = p_quarter
then num else 0
end) as num_quarter_1,
sum(case when year(curdate() - interval 1 quarter) = p_year and quarter(curdate() - interval 1 quarter) = p_quarter
then num else 0
end) as num_quarter_2,
sum(case when year(curdate() - interval 2 quarter) = p_year and quarter(curdate() - interval 2 quarter) = p_quarter
then num else 0
end) as num_quarter_3,
sum(case when year(curdate() - interval 3 quarter) = p_year and quarter(curdate() - interval 3 quarter) = p_quarter
then num else 0
end) as num_quarter_4
from production p
group by person_id;