mysql如何从多个数据中提取数据并总结

Question

对于mysql来说很新，并且很难制定这种类型的查询。

下一个表（表称为TableX的），让我们说结构如下

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

像... ..等等

我知道我可以做简单的 选择总和（numberofUser）从tableX其中服务器像'server1'按时间戳顺序desc限制100; 以获得服务器1的最后100个时间戳的用户总数

但是，您将如何为所有3台服务器执行此操作？我想为每个服务器的100个时间戳记汇总所有3个服务器的结果。只是不太确定如何执行此操作。请帮忙。

Answer 1

使用由

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

，并限制你的时间周期组

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

所有服务器的总简直是

select sum(numberofUser) 
from tableX 

在过去的10列Server1和Server2上的

驻颜为单个服务器

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 

或全为2服务器

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