Learn how relationships depend on essential “key” fields, then plan the relationships you’ll use in the sample app. In this video, you will: * Understand a common type of relationship: learn about the “one-to-many” relationship (0:38) * Define primary and foreign keys: see how a lack of key fields can lead to messy data (1:00) * Find your relationships: determine how your app’s tables should relate to each other (2:40)