การออกแบบสคีมา Prisma และการย้ายข้อมูล

Welcome back! In this lesson, we'll dive into designing your database schema using Prisma Schema Language and managing changes with migrations.

The schema.prisma file is the heart of your Prisma setup. It's a single source of truth for your database schema and how your application models interact with it.

Every schema.prisma file starts with two main blocks: datasource and generator.

• datasource: Defines your database connection (e.g., PostgreSQL, MySQL, SQLite).
• generator: Specifies which Prisma Client to generate, allowing you to interact with your database in a type-safe way.

Here's a basic structure:

After the core blocks, you define your models. A Prisma model maps directly to a table in your database and represents the structure of your data.

The model keyword is used, followed by the model's name (singular, PascalCase, e.g., User or Product).

Inside each model, you define fields, which correspond to columns in your database table. Each field has a name and a data type.

Prisma supports common scalar types like String, Int, Boolean, DateTime, Float, Json, and more. For example, id is often a String or Int.

Fields can have modifiers and attributes to add extra meaning or constraints:

• ? (Optional): Makes a field nullable.
• [] (List): Indicates a list of values (e.g., String[]).
• @id: Marks a field as the primary key.
• @unique: Ensures all values in this field are unique.
• @default(): Sets a default value.
• @updatedAt: Automatically updates a DateTime field on every record update.

Databases are all about related data! Prisma makes it easy to define relationships between your models, like a user having many posts (one-to-many).

You define a relation by linking fields between models using the @relation attribute. This attribute takes arguments like fields (the foreign key) and references (the primary key it refers to).

As your application grows, your database schema will change. Migrations are how Prisma tracks these changes and applies them to your actual database in a controlled, versioned way.

Prisma Migrate generates SQL files based on the differences between your schema.prisma and your current database state, ensuring your database evolves predictably.

To create a new migration, you use the Prisma CLI command npx prisma migrate dev. You should give your migration a descriptive name.

This command does three things:

1. Compares your schema.prisma to the database.
2. Generates a new migration file (SQL) if there are changes.
3. Applies the new migration to your development database.

Try it after making a change to your schema:

Besides prisma migrate dev for development, there are other commands:

• npx prisma migrate deploy: Applies all pending migrations to the database. This is typically used in production environments.
• npx prisma db push: Pushes the current schema state to the database without creating a migration file. Useful for rapid prototyping in development when you don't need migration history.

Choose the right command for your workflow!

You've just added a new field role to your User model in schema.prisma and want to apply this change to your development database while also creating a migration file to track this change. Which command should you use?

Great job! You've learned how to design your database with Prisma Schema Language and manage its evolution with migrations.

• The schema.prisma file is your single source of truth for database structure.
• Models define tables, and fields define columns with various types and attributes.
• Relations connect your models, reflecting real-world data links.
• Prisma Migrate helps you track and apply schema changes reliably across environments.

Next, we'll learn how to perform CRUD operations (Create, Read, Update, Delete) using the Prisma Client.