MySQL GROUP BY如何从第一个元素中获取数据[重复]

Question

我有下一张数据表：

然后我运行这个查询：

select *, UNIX_TIMESTAMP(`time`) AS `timeu`, AVG(`value`) AS `valuea`
from `values` 
group by `currency`, DATE(`time` - interval 7 day) 
order by `id` asc 

结果我得到

如您所见，ids 是：1, 2, 3, 4, 11, 12。我想要1, 2, 3, 4, 5, 6 - 我怎样才能简单地构建我的查询来做到这一点？

Answer 1

你不会做group by。

我怀疑你可以使用相关子查询做你想做的事：

select v.*, UNIX_TIMESTAMP(`time`) AS `timeu`,
      (SELECT AVG(`value`)
       from values v2
       where v2.currency = v.currency and
             v2.time >= v2.time - interval 7 day
      ) as `valuea`
from `values` v
order by `id` asc ;