Create a ROLLING sum over a period of time in mysql

Question

I have a table with columns date and time_spent. I want to find for each date D the sum of the values of \'time_spent\' for the period of time : (D

Answer 1

Here is another solution

SELECT r1.date, r1.time_spent, 
   ( SELECT SUM(time_spent) 
     FROM rolling_total AS r2
     WHERE datediff(r1.date, r2.date) 
     BETWEEN 0 AND 7
   ) AS rolling_week_total
FROM rolling_total AS r1  
ORDER BY r1.date
LIMIT 8

Answer 2

And one more solution

SELECT r1.date, r1.time_spent, sum(r2.time_spent) AS rolling_week_total
FROM rolling_total AS r1 JOIN rolling_total AS r2
    ON datediff(r1.date, r2.date) BETWEEN 0 AND 7
GROUP BY r1.date
ORDER BY r1.date
LIMIT 8

Answer 3

Here you go:

select
t.*,
@total:=@total + t.time_spent - coalesce(t2.time_spent, 0) as your_total_over_last_7_days
from
rolling_total t
left join rolling_total t2 on t.date = t2.date + interval 8 day
, (select @total:=0) v
order by t.`date` 

• see it working live in an sqlfiddle.