Hi Yann,

Doing a one-to-many link (customer to transactions) could potentially be slower than a many-to-one link (transactions to customer) because the transaction file could be re-read multiple times on a one-to-many scenario.

A practical reason for the linking difference is that if you wanted to prit customer that do not have any transactions, you have to drive the report (link from) from the customer master file, as all customers are read that way. If you only want to print the transactions and associated 'customer master' information, such as the name or address, then it is better to drive the report from the transaction file.