mysql - 如何创建显示过去 4 个季度数据的 View ？

Question

我的环境是5.1.72-community。

我有一个名为“生产”的表，例如:

 id, person_id, num, p_year, p_quarter
 1, 1, 43, 2018, 2 
 2, 1, 92, 2018, 1
 3, 1, 108, 2017, 4
 4, 2, 41, 2018, 2
 ...

到“2018-04-14”时，我们知道季度=2，年份=2018。我定义quarter_1是当年的当前季度，quarter_2是上一季度，依此类推。现在我想创建一个像这样的 View :

 person_id, num_quarter_1, num_quarter_2, num_quarter_3, num_quarter_4
 1, 43, 92, 108, 0
 2, 41, 0, 0, 0

这样，如果该季度没有num，则填0。

如何创建该 View ？

Answer 1

嗯。如果我将“最后四个季度”解释为“数据中的最后四个季度”，那么这是一种方法。

首先，您可以通过以下方式获得四个季度:

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

您可以使用变量枚举它们:

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

然后，您可以在查询中使用它来透视数据:

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;

编辑:

如果您根据当前季度定义季度，则可以执行类似的操作:

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;

还有其他方法，例如:

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;