Drizzle is a TypeScript ORM that aims to maintain type safety while using a familiar SQL syntax, and it can be used in conjunction with PlanetScale to create virtual relationships between tables. Foreign key constraints are not allowed on PlanetScale, but Drizzle's virtual relationships can achieve similar results without them. To establish these relationships, you need to use the `references` method on fields to specify the related entity and its field, and then define the relationship using the `relations` function. This allows for more flexibility in querying related data without relying on foreign key constraints. Additionally, when cascading actions are needed, it's up to the developer to handle these tasks through code instead of relying on database constraints.