Schema in Knex.js

Schema is an important concept in Knex.js, a query builder for Node.js, that helps you define and manage database tables and their relationships. In this guide, we'll dive into the basics of schema in Knex.js and how you can use it to create and modify your database's schema.

What is Schema?

A schema is a way of organizing and describing the structure of a database. It defines the tables, columns, indexes, relationships, and constraints that make up the database's structure. In Knex.js, a schema consists of one or more table definitions and any associated constraints or indexes.

Creating a Table

To create a table in Knex.js, you can use the knex.schema.createTable() method:

knex.schema.createTable('users', function (table) {
  table.increments('id')
  table.string('name')
  table.string('email').unique()
  table.timestamps()
})

This will create a new table called users with an auto-incrementing id column, name and email columns, and timestamp columns for created_at and updated_at. You can add additional columns or modify the existing ones as needed.

Modifying a Table

You can also modify an existing table's schema using the knex.schema.table() method:

knex.schema.table('users', function (table) {
  table.boolean('active').defaultTo(false)
  table.dropColumn('email')
})

This will add a new active column to the users table and remove the email column. You can use any of the supported column types and modifiers in Knex.js to make additional modifications.

Dropping a Table

To drop a table in Knex.js, you can use the knex.schema.dropTableIfExists() method:

knex.schema.dropTableIfExists('users')

This will delete the users table if it exists. You can also add multiple table names to drop multiple tables at once.

Summary

In summary, schema in Knex.js is a way to define and manage the structure of your database tables. You can use the knex.schema object to create, modify, and delete tables as needed. With this powerful tool, you can easily manage your database schema in a declarative way and ensure your database is always in the right state.