合并两个查询以在MySQL中获得单个结果

如何解决合并两个查询以在MySQL中获得单个结果

我有以下两个代码，我需要用'for_2018_19'除以'total'来获得百分比。我不知道如何合并它们并获得单个结果，即百分比。

select sum(maternities) as total from merged
where City = 'Jeza' and Group = 'UnkNown';

select sum(Maternities) as for_2018_19 from merged
where Year = '2016/17') percentage ;

解决方法

您将bth查询用作唯一回传单个数据的子查询

但是yu应该记住，group是保留字，应该避免使用

SELECT
(select sum(maternities)  from merged
where City = 'Jeza' and `Group` = 'Unknown')/
(select sum(Maternities)  from merged
where Year = '2016/17') as percentage

,

您可以下一步：

select 
    -- divide partial sum by total
    sum(if(Year = '2016/17',maternities,0)) / 
    sum(if((City = 'Jeza' and `Group` = 'Unknown'),0))
from merged;

,

您还可以使用：

select sum(Maternities)*100.0/(select sum(maternities) as total from merged
where City = 'Jeza' and Group = 'Unknown') as percent from merged
where Year = '2016/17'

,

select b.for_2018_19 / a.total
from ( select sum(maternities) as total 
       from merged
       where City = 'Jeza' 
       and Group = 'Unknown' ) a,(    select sum(Maternities) as for_2018_19 
       from merged
       where Year = '2016/17'
  ) b