SQL选择列多次不同的条件

Question

我有一个事件表，其中包含事件中受伤人数的列和事件中死亡人数的列。 Incident 表与 Participants 表链接，您可以在其中找到一个人的年龄列，还有另一个表 ParticipantTypes 的列类型（例如，man（id = 1），woman（id = 2））。 所以，我想检索受伤的列号，在类型是男人的地方被杀的列号，在他们旁边受伤的列号，在类型是女人的地方被杀的列号，所有按年龄分组。

select    
ip.age as age, 
sum(i.number_injured) as injured,
sum(i.number_killed) as killed
from Incidents i
inner join Participants ip on i.id = ip.incident_id
inner join ParticipantTypes ipt on ip.type_id = ipt.id
where ipt.id = 1
group by ip.age

以下查询仅适用于 ParticipantTypes.type = 1 (man)

我想要这样的东西

select    
ip.age as age, 
sum(i.number_injured) as injured where ipt.id = 1,
sum(i.number_killed) as killed where ipt.id = 1, 
sum(i.number_injured) as injured where ipt.id = 2,
sum(i.number_killed) as killed where ipt.id = 2, 
from Incidents i
inner join Participants ip on i.id = ip.incident_id
inner join ParticipantTypes ipt on ip.type_id = ipt.id
group by ip.age

Answer 1

select    
    ip.age as age, 
    sum(case when ipt.id=1 then i.number_injured    else 0 end)     as injured_man,
    sum(case when ipt.id=1 then i.number_killed     else 0 end)     as killed_man,
    sum(case when ipt.id=2 then i.number_injured    else 0 end)     as injured_woman,
    sum(case when ipt.id=2 then i.number_killed     else 0 end)     as killed_woman
 from 
    Incidents i
inner join 
    Participants ip on i.id = ip.incident_id
inner join 
    ParticipantTypes ipt on ip.type_id = ipt.id
group by ip.age

示例结果：

age         injured_man killed_man  injured_woman killed_woman 
----------- ----------- ----------- ------------- ------------ 
         30          10           1             3            1 
         31          12           1             1            6 
         32          14           2             4            4 

Answer 2

试试这个....

select    
ip.age as age, 
sum(case when ipt.id=1then i.number_injured else 0                
end) as injured_by_man,
sum(case when ipt.id=1then i.number_killed else 0  
end) as killed_by_man,
sum(case when ipt.id=2 then i.number_injured else 0 
end) as injured_by_woman,
sum(case when ipt.id=2 then i.number_killed else 0 
end) as killed_by_woman

from Incidents i
inner join Participants ip on i.id = ip.incident_id
inner join ParticipantTypes ipt on ip.type_id = ipt.id
group by ip.age

Answer 3

select    
ip.age as age, 
sum(if(ipt.id=1,i.number_injured,0)) as injured_by_man,
sum(if(ipt.id=1,i.number_killed,0) as killed_by_man,
sum(if(ipt.id=2,i.number_injured,0)) as injured_by_woman,
sum(if(ipt.id=2,i.number_killed,0)) as killed_by_woman

from Incidents i
inner join Participants ip on i.id = ip.incident_id
inner join ParticipantTypes ipt on ip.type_id = ipt.id
group by ip.age

注意：上述代码未经测试。它可能包含小的语法错误。

Answer 4

您在inner join 和where 中都过滤掉了ipt.id = 1 条件下的woman 记录。

此外，您按age 分组，这不是您想要的，正如我从问题中理解的那样。所以，你的最终查询应该是。

编辑：根据有问题的更新详细信息，以下是查询

select
    ip.age,
    sum(case when ipt.id =1 then i.number_injured else 0 end) as men_injured,
    sum(case when ipt.id =1 then i.number_killed else 0 end) as men_killed,
    sum(case when ipt.id =2 then i.number_injured else 0 end) as women_injured,
    sum(case when ipt.id =2 then i.number_killed else 0 end) as women_killed
from Incidents i
       inner join Participants ip on i.id = ip.incident_id
       inner join ParticipantTypes ipt on ip.type_id = ipt.id
group by ip.age