🔍 What is Alembic?
Alembic is a lightweight database migration tool that works with SQLAlchemy.
Migration tools allow you to plan, transfer, and upgrade your database schema over time.
SQLAlchemy alone can create tables but cannot modify them after creation.
Alembic enables us to add new columns, modify tables, or update schema without deleting existing data.
For example, if your application evolves and you need a new field in your users table, Alembic allows you to do this safely.
⚙️ How Does Alembic Work?
Alembic works by creating migration scripts that define changes to your database.
You create a migration environment once.
Whenever your database schema needs to change, Alembic generates migration scripts.
These scripts can be executed to apply changes to your database safely.
Alembic is especially useful in production applications because database changes can happen while preserving existing data.
📝 Example: Adding a Phone Number Column
Imagine we have a users table with the following data:
ID (Primary Key) | First Name | Last Name | Hashed Password | |
|---|---|---|---|---|
1 | Example | User | $2b$12$Xk9LmPqRsT12345 |
We want to add a phone number column to this table.
Instead of deleting the table or losing data, Alembic allows us to add this column safely.
🔧 Benefits of Alembic
Enables continuous database evolution as your application grows.
Works with tables already containing data.
Helps manage versioning of your database schema.
Integrates seamlessly with FastAPI and SQLAlchemy projects.