如何连接表格而不是重复数据

Question

我是新来的，因为我在学习SQL，而且遇到了一个我无法解决的问题。请帮帮我。 我有两个表结果和收入与数据，看到表的截图。 https://www.box.com/s/5c1ah5qi9jg5ty499wvs

我想加入这些表格，但由于carthesian产品的某些数据被添加了两次。这里是我的代码：

select o.point, o.date, sum(out), sum(inc) from outcome o left join income i on o.point=i.point and o.date=i.date 
group by o.point, o.date 
union 
select i.point, i.date, sum(out), sum(inc) from income i left join outcome o on o.point=i.point and o.date=i.date 
group by i.point, i.date 

有什么建议吗？提前致谢。

G.

Answer 1

我想你想要的是一个full outer join，而不是union：

select coalesce(o.point, i.point) as point, 
     coalesce(o.date, i.date) as date, 
     sum(out), sum(inc) 
from outcome o full outer join 
    income i 
    on o.point=i.point and o.date=i.date 
group by coalesce(o.point, i.point) , coalesce(o.date, i.date) 

或者，你可能想要做的两个表之间的union，然后汇总，如：

select point, date, sum(out), sum(inc) 
from ((select o.point, o.date, out, NULL as inc 
     from outcome 
    ) union all 
     (select i.point, i.date, NULL as out, inc 
     from income 
    ) 
    ) io 
group by point, date 

即使每个表中有给定点/ dat的多行，该版本也能正常工作e组合。