Scenario: In exercise 2.9 on Using Tags, we mentioned that Craig's friend John had been doing a great job spreading the word for Craig's services. Craig was curious how much money he had made from John's referrals, so we added the tag to a handful of transactions. Now Craig has realized that in addition to those few clients, John was also instrumental in landing Amy's Bird Sanctuary, which Craig has done a lot of work for. Let's see how we can add John's tag to all those transactions at once.