Question

相当新的mysql并且无法制定此类查询。

在一个表（名为tableX的表）下，假设结构如下所示

server       date           numberofUser
 server1   timestamp        3
 server2   timestamp        2
 server3   timestamp        7
 server1   timestamp        2
 server2   timestamp        8
 server3   timestamp        4

......等等

我知道我可以做得很简单从tableX中选择sum（numberofUser），其中服务器如'server1'按时间戳desc限制100; 获取server1的最后100个时间戳的用户总数

但是你会如何为所有3台服务器执行此操作？我想为每个服务器聚合100个时间戳的所有3台服务器的结果..只是不太确定如何做到这一点。请帮忙。

Answer 1

使用分组

select sum(numberofUser) , server
from tableX 
group by server

并限制您的时间段

select sum(numberofUser) , server
from tableX 
where timestamp between 'your_date_min' AND 'your_date_max'
group by server

所有服务器的总数只是

select sum(numberofUser) 
from tableX

表示server1和server2的最后10行

单个服务器的总计

select sum(numberofUser), server from (
  (select  server,   date, numberofUser from tableX 
  where server = 'server1'
  order by date limit 10 )
  union 
  (select  server,  date, numberofUser from tableX 
  where server = 'server2'
  order by date limit 10 )) as t
group by server

或2服务器的总数

select sum(numberofUser) from (
    (select  server,   date, numberofUser from tableX 
    where server = 'server1'
    order by date limit 10)
    union
   ( select  server,   date, numberofUser from tableX 
    where server = 'server2'
    order by date limit 10 )) as t

mysql如何从多个和sum中提取数据

1 个答案: