Field note · September 9, 2023
Reader question — One metric, one definition
The reason three dashboards show three different revenue numbers is never a bug. It is three people who each wrote their own definition, and all of them were reasonable.
Reader question on One metric, one definition, and the answer belongs somewhere more findable than an email.
The reason three dashboards show three different revenue numbers is never a bug. It is three people who each wrote their own definition, and all of them were reasonable.
The question was, roughly, "when does this stop applying?" — which is the right question and the one lessons routinely fail to answer. Every technique has a range of validity, and stating it is what separates a lesson from a recipe.
It sits in the Modelling the warehouse module. The exercise is a thinking one rather than a query one — some of this material is about deciding what to compute, and that does not need a keyboard.
Ordering matters here more than in most courses. It follows Why your query costs what it costs and leads into Joins that do not fan out, and reading it out of sequence mostly works but costs you the setup.
Free means free, and it also means we can rewrite it whenever it is wrong. No edition, no errata PDF, nothing to repurchase. The whole course is 36 lessons and the fixes land the day we find them.