Create New Tables and Models With Deno Database Migration

Quack & Crumb Model#

The best way to start on the new namespaces is to get the migration out of the way. In this migration we will be creating both the quack and crumb tables, so let's dive into it!

Migration#

Create a new migration using the Nessie CLI and populate it with the following code:

deno run -A --unstable https://deno.land/x/nessie@2.0.7/cli.ts make:migration create_quack_crumb_table

        created_by VARCHAR(30) REFERENCES duck(id) ON DELETE CASCADE,

Similar to the first two migrations the class and methods are the same, except that we now have the table creations wrapped in a transaction. As we briefly discussed earlier, when we learned about Nessie, we want to make a transaction when we are handling multiple changes or multiple calls to the database. The reason for this is so that should, for example, the quack table succeed, but the crumb table fail, we don't get stuck in the middle of an uncompleted migration. A migration should either be completely successful, or not make any changes at all.

We are also setting a couple of foreign keys and relations between the tables. In the quack table, the created_by column is related to the id in the duck table, and the crumb table is simply a reference table between duck andquack giving us a "many-to-many" relationship.

As our application serves as a minimal example, we don't really care about data retention, so when a record gets deleted, we simply remove the related records. This should obviously not be the case for real-life applications.

Models#