Você precisa
group os dados; por exemplo:select c.name,c.id,sum(o.amount) as amount
from CUSTOMERS c
inner join ord o on c.id=o.customer_id
group by c.id, c.name
group os dados; por exemplo:select c.name,c.id,sum(o.amount) as amount
from CUSTOMERS c
inner join ord o on c.id=o.customer_id
group by c.id, c.name
