magento-average-orders-per-hour.sql

select
    `Time Period`,
    round(avg(num), 1) `Average Number of Orders`
from (
    select
        date_format(date_sub(o.created_at, interval 8 hour), "%l:00 - %l:59 %p PST") `Time Period`,
        count(*) num,
        date_format(date_sub(o.created_at, interval 8 hour), "%H") sort
    from sales_flat_order o
    where o.created_at > '2016-01-01 00:00:00'
    and o.created_at < '2016-02-01 00:00:00'
    group by date_format(date_sub(o.created_at, interval 8 hour), "%Y-%m-%d-%H")
) t 
group by `Time Period`
order by sort;