SQL獲得數計每分鐘

Question

我有這樣一個數據集：

id  name  updated_at 
1  test1  2014-06-30 09:00:00 
1  test2  2014-06-30 09:01:10 
1  test3  2014-06-30 09:01:23 
1  test4  2014-06-30 09:01:43 
1  test5  2014-06-30 09:02:02 
1  test6  2014-06-30 09:02:34 
1  test7  2014-06-30 09:03:22 
1  test8  2014-06-30 09:03:28 

我需要一分來獲得行的計數的最後十分鐘。所以它應該總是返回十個數字，即最後更新的行數。任何想法如何做到這一點和有效？

Answer 1

去年10結果

http://sqlfiddle.com/#!9/3d586/22

--get the minute component of the update time 
select minute(updated_at) as Sec 
--count the number of records which have this minute 
, count(1) as Cnt 
from myTable 
--use group by to ensure we return 1 row per minute 
group by minute(updated_at) 
--list from most recent working backwards 
order by minute(updated_at) desc 
--return up to 10 results 
limit 10 

結果最後10分鐘

http://sqlfiddle.com/#!9/3d586/26

--get the minute component of the update time 
select minute(y.d) as Min 
--count the number of records which have this minute 
--use m.id instead of 1 or * to ensure where there's no result from myTable 
--we don't count any rows 
, count(m.id) as Cnt 
from 
(
    --get the current date's minute, offset by a given amount 
    select date_add(now(), interval -x.a minute) d 
    from 
    (
     --the list of given amounts by which to offset the above date 
     select 0 a 
     union select 1 
     union select 2 
     union select 3 
     union select 4 
     union select 5 
     union select 6 
     union select 7 
     union select 8 
     union select 9 
    ) x 
) y 
--left join to ensure the above list drives which results we get, 
--regardless of whether there are matching entries in myTable 
left outer join myTable m 
--join on the minute of each date 
on minute(m.updated_at) = minute(y.d) 
--use group by to ensure we return 1 row per minute 
group by minute(y.d) 
--list from most recent working backwards 
order by minute(y.d) desc 

Answer 2

由於您想插值，因此它很快變得更加複雜。最後十分鐘內每分鐘創建一個派生表格作爲一行可能是最簡單的，然後將它們留在那裏。下面是做這件事：

select minute(now() - interval m minute) 'minutes ago', count(case when t.updated_at is not null then t.updated_at end) 
from 
    (select minute(now()) m 
    union 
    select minute(now() - interval 1 minute) m 
    union 
    select minute(now() - interval 2 minute) m 
    union 
    select minute(now() - interval 3 minute) m 
    union 
    select minute(now() - interval 4 minute) m 
    union 
    select minute(now() - interval 5 minute) m 
    union 
    select minute(now() - interval 6 minute) m 
    union 
    select minute(now() - interval 7 minute) m 
    union 
    select minute(now() - interval 8 minute) m 
    union 
    select minute(now() - interval 9 minute) m 
    union 
    select minute(now() - interval 10 minute) m 
) q 
    left join myTable t 
    on q.m = minute(t.updated_at) 
     and t.updated_at >= now() - interval 10 minute 
    group by m 
    order by m desc 

這裏有一個小提琴，但你必須改變模式（剛加入某一個空格），爲了重建它來得到準確的結果：

http://sqlfiddle.com/#!9/f3320/1