Join tables without inflating metrics

Joining an order to two items creates two result rows. That is correct, but the order total repeats. Identify what a row represents and compute each measure at the right grain.

After a one-to-many join, a parent repeats per child. Count distinct parent keys and sum item values at item grain.

Join tables without inflating metrics: After a one-to-many join, a parent repeats per child. Count distinct parent keys and sum item values at item grain.