Hoe maak je een weergave met gegevens over de laatste 4 kwartalen?

Hmmm. Als ik "laatste vier kwartalen" interpreteer als "de laatste vier kwartalen die in de gegevens staan", dan is hier één methode.

Ten eerste kun je de vier kwartalen krijgen door te doen:

select distinct p_year, p_quarter
from production p
order by p_year desc, p_quarter desc
limit 4;

Je kunt ze opsommen met behulp van variabelen:

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

Vervolgens kunt u dit in een query gebruiken om de gegevens te draaien:

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;

BEWERKEN:

Als u de kwartalen definieert op basis van het huidige kwartaal, kunt u iets soortgelijks doen:

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;

Er zijn andere benaderingen, zoals:

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;