O exemplo do MySQL abaixo cobre uma janela deslizante de 7 dias:
select t1.`DATE`, AVG(t2.`VALUE`) as MV_AVG
from MyTable t1
left outer join MyTable t2
on t2.`DATE` between DATE_ADD(t1.`DATE`, INTERVAL -6 DAY)
and t1.`DATE`
group by t1.`DATE`
Exemplo do SQL Fiddle
Saída:
| DATE | MV_AVG |
------------------------------------------------
| August, 12 2012 20:00:00+0000 | 160 |
| August, 19 2012 20:00:00+0000 | 52 |
| August, 26 2012 20:00:00+0000 | 63 |
| September, 03 2012 20:00:00+0000 | 41 |
| September, 09 2012 20:00:00+0000 | 30.5 |
| September, 16 2012 20:00:00+0000 | 20 |
| September, 23 2012 20:00:00+0000 | 285 |
| September, 24 2012 20:00:00+0000 | 152.5 |
| September, 30 2012 20:00:00+0000 | 52.5 |
| October, 08 2012 20:00:00+0000 | 41 |
| October, 14 2012 20:00:00+0000 | 6037 |
| October, 15 2012 20:00:00+0000 | 6610 |
| October, 16 2012 20:00:00+0000 | 5624.6667 |
| October, 21 2012 20:00:00+0000 | 1649.6667 |
| October, 28 2012 20:00:00+0000 | 31 |
| November, 04 2012 19:00:00+0000 | 10 |
