Migrations for schema changes in Express - Mini Project: Build & Apply

Migrations for schema changes

📖 Scenario: You are building a simple Express app that stores user information in a database. Over time, you need to change the database schema safely without losing data. This project will guide you through creating a migration script to update the schema.

🎯 Goal: Create a migration script using Express and a migration tool to add a new column age to the users table.

📋 What You'll Learn

Create an initial users table schema

Add a configuration variable for the new column

Write a migration script to add the new column

Complete the migration setup to run the migration

💡 Why This Matters

🌍 Real World

Migrations help update database schemas safely as apps grow and change, avoiding data loss.

💼 Career

Knowing migrations is essential for backend developers to manage database changes in production environments.

1

Create initial users table schema

Create a migration file that defines a users table with columns id (integer, primary key) and name (string). Use the exports.up function to create the table.

Express

// Your migration code here
exports.up = function(knex) {
  // Create users table
};

exports.down = function(knex) {
  // Drop users table
};

Need a hint?

Use knex.schema.createTable inside exports.up to create the table with id and name.

2

Add configuration for new column

Create a constant called newColumn and set it to the string 'age'. This will be the name of the new column to add.

Express

exports.up = function(knex) {
  return knex.schema.createTable('users', function(table) {
    table.increments('id').primary();
    table.string('name');
  });
};

exports.down = function(knex) {
  return knex.schema.dropTable('users');
};

// Define new column name
// Your code here

Need a hint?

Define const newColumn = 'age'; above the migration functions.

3

Write migration to add new column

Modify the exports.up function to add the new column age as an integer to the existing users table using knex.schema.table. Use the newColumn constant for the column name.

Express

const newColumn = 'age';

exports.up = function(knex) {
  // Add new column to users table
  // Your code here
};

exports.down = function(knex) {
  return knex.schema.dropTable('users');
};

Need a hint?

Use knex.schema.table('users', ...) to add the age column as integer in exports.up. Remove it in exports.down.

4

Complete migration setup

Export the migration functions exports.up and exports.down so they can be run by the migration tool. Ensure the file exports both functions correctly.

Express

const newColumn = 'age';

// Export migration functions
// Your code here

Need a hint?

Make sure both exports.up and exports.down are defined and exported.