mysql - 如何在同一个结果表中包含来自两个查询的信息？

Question

我有以下问题:

select year, avg(value) as winter_avg_Miami from AP_DATA where substring(series_id, 8) ='killowatts' and  substring(series_id, 3,5) = 'Miami' and period IN ('M10','M11','M12') group by year;
select year, avg(value) as winter_avg_notMiami from AP_DATA where substring(series_id, 8) = 'killowatts' and  substring(series_id, 3,5) != 'Miami' and period IN ('M10','M11','M12') group by year;

我想要做的不是得到两个不同的表，一个像:

year       winter_avg_Miami
2000             28.1
2001             30.2

还有另一个表:

year        winter_avg_notMiami
2000             40.1
2001             50.2

我只想将所有信息放在一张表中，例如:

year       winter_avg_Miami  winter_avg_notMiami
2000             28.1              40.1 
2001             30.2              50.2

我该如何编写查询才能完成此任务？

Answer 1

您可以在 avg 聚合中使用 case 语句:

select year, 
   avg(case when substring(series_id, 3,5) = 'Miami' then value end) as winter_avg_Miami,
   avg(case when substring(series_id, 3,5) != 'Miami' then value end) as winter_avg_notMiami 
from AP_DATA 
where substring(series_id, 8) ='killowatts'
    and period IN ('M10','M11','M12') 
group by year

• Condensed SQL Fiddle Demo