knex

What is knex?

Knex.js is a SQL query builder for JavaScript, which works with multiple database systems like PostgreSQL, MySQL, SQLite3, and Oracle. It allows for building and executing SQL queries in a readable and programmatic way, handling connections and transactions, and seeding and migrating databases for development purposes.

What are knex's main functionalities?

Query Building

Builds a SQL query to select all columns from the 'users' table where the 'id' is 1.

knex.select('*').from('users').where('id', 1)

Schema Building

Creates a new table called 'users' with an auto-incrementing 'id' column, a 'name' column of string type, and timestamp columns for 'created_at' and 'updated_at'.

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

Transaction Support

Performs a transaction to insert multiple records into the 'books' table. If any part of the transaction fails, all changes are rolled back.

knex.transaction(function(trx) { const books = [{title: 'Canterbury Tales'}, {title: 'Macbeth'}]; return trx.insert(books).into('books'); })

Raw Queries

Executes a raw SQL query, selecting all columns from the 'users' table where the 'id' is 1, with parameter binding.

knex.raw('SELECT * FROM users WHERE id = ?', [1])

Seeding

Defines a seed file that first clears the 'users' table and then inserts new records into it.

exports.seed = function(knex) { return knex('users').del().then(function() { return knex('users').insert([{name: 'Alice'}, {name: 'Bob'}]); }); }

Migrations

Defines a migration file with an 'up' method to create a new 'users' table and a 'down' method to drop the 'users' table.

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

Other packages similar to knex

sequelize

Sequelize is an ORM (Object-Relational Mapping) library for Node.js. It provides a higher-level abstraction for database interactions and supports multiple dialects. Unlike Knex, which is primarily a query builder, Sequelize allows for defining models and relationships directly in JavaScript.

typeorm

TypeORM is an ORM for TypeScript and JavaScript (ES7, ES6, ES5). It supports the Data Mapper and Active Record patterns and works with SQL databases. It provides more advanced ORM features compared to Knex, such as automatic migration generation and support for decorators.

bookshelf

Bookshelf.js is a JavaScript ORM for Node.js, built on the Knex SQL query builder. It features a simple and intuitive API and supports relations, eager and lazy loading, model events, and plugins. It's more ORM-focused than Knex but uses Knex under the hood for query building.