MySQL GROUP BY 如何从第一个元素获取数据

Question

这个问题已经有答案了:

Groupwise maximum (5 个回答)

已关闭 8 年前。

我有下一个包含数据的表:

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 id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

您不会执行分组依据。

我怀疑你可以使用相关子查询来做你想做的事情:

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 ;