Previous module: Module 6, WHERE and HAVING: filtering before and after GROUP BY.
Two people can calculate a conversion rate and still get different numbers. One person might count orders while the other counts customers. They might also use different dates to decide which rows belong in January.
The SQL can be correct in both cases because the problem starts with the metric definition. We still need to choose the numerator, denominator, counting unit, and time period.
In this module, we’ll use a January purchase cohort to compare two definitions. First, we’ll check what happens when the numerator and denominator use different date columns. After that, we’ll compare an order completion rate with a customer completion rate.
