I have a large database, Where I have two tables claims and invoices. In invoice table when I run the query

select sum(amount) from invoices.
Gives me value of 207859507

However when I join two tables and group then by one variable such as mileage in claim table

SELECT c.mileage, SUM(i.amount) AS amount
FROM claims c
INNER JOIN invoices i
ON i.ID = c.ID AND i.accident_date = c.accident_date
GROUP BY mileage

it gives me a greater value i.e. 214110863...

But conceptually the join must have smaller value then the other query