Practice: Change DB Structure in "Live" Project

In this lesson, you will see an example of restructuring the database.

Imagine a scenario:

1. You have Posts that belong to one Category
2. At some point, you decide to have multiple categories

So, from one-to-many to many-to-many. But the project is already live. What should you do?

Step 1: What Changes Are Needed?

First, let's identify the behavior changes.

Change 1. When viewing a post, instead of showing a single category, it should list all categories with a foreach loop.

Change 2. When showing posts by a category, the query should also be changed.

Where do we start, and how do we do it safely?

Step 2: Automated Tests

Let's start with a different question: "How will you test everything after you make the changes in the code?"

To answer that question, I have a personal rule of thumb. For making any big structure refactorings in a big project: first, write automated tests.

You need to write tests of all the features and how...