If this is the same table, then the same columns across the board for all alias instances. I would ensure an index on (channel_id, entry_id, field_id_117 ) if possible. Another index on (author_id) for the prequery of order totals
Then, start first with what will become an inner query doing nothing but a per customer sum of order amounts.. Since the join is the "author_id" as the customer ID, just query/sum that first. Not completely understanding the (what I would consider) poor design of the structure, knowing what the "Channel_ID" really indicates, you don't want to duplicate summation values because of these other things in the mix.
select
o.author_id,
sum( o.field_id_22 ) as totalOrders
FROM
exp_channel_data customers o
where
o.channel_id = 3
group by
o.author_id
If that is correct on the per customer (via author_id column), then that can be wrapped as follows
select
PQ.author_id CustomerID,
c.field_id_122 CompanyName,
PQ.totalOrders
from
( select
o.author_id,
sum( o.field_id_22 ) as totalOrders
FROM
exp_channel_data customers o
where
o.channel_id = 3
group by
o.author_id ) PQ
JOIN exp_channel_data c
on PQ.author_id = c.field_id_117
AND c.channel_id = 7