从另一个查询中获取最大值

Select product_name,max(total_amount) from(
select
products.product_name,
sum(product_invoice.product_amount) as total_amount
from product_invoice
inner join products
on product_invoice.product_id = products.product_id
inner join invoices
on product_invoice.invoice_id = invoices.invoice_id
where month(invoices.invoice_date) = 2
group by products.product_name
) outputTable