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.

README

knex.js

A SQL query builder that is flexible, portable, and fun to use!

A batteries-included, multi-dialect (MSSQL, MySQL, PostgreSQL, SQLite3, Oracle (including Oracle Wallet Authentication)) query builder for Node.js, featuring:

• transactions
• connection pooling
• streaming queries
• both a promise and callback API
• a thorough test suite

Node.js versions 10+ are supported.

• Take a look at the full documentation to get started!
• Browse the list of plugins and tools built for knex
• Check out our recipes wiki to search for solutions to some specific problems
• In case of upgrading from an older version, see migration guide

You can report bugs and discuss features on the GitHub issues page or send tweets to @kibertoad.

For support and questions, join our Gitter channel.

For knex-based Object Relational Mapper, see:

• https://github.com/Vincit/objection.js
• https://github.com/mikro-orm/mikro-orm
• https://bookshelfjs.org

To see the SQL that Knex will generate for a given query, you can use Knex Query Lab

Examples

We have several examples on the website. Here is the first one to get you started:

const knex = require('knex')({
  client: 'sqlite3',
  connection: {
    filename: './data.db',
  },
});

try {

  // Create a table
  await knex.schema
    .createTable('users', table => {
      table.increments('id');
      table.string('user_name');
    })
    // ...and another
    .createTable('accounts', table => {
      table.increments('id');
      table.string('account_name');
      table
        .integer('user_id')
        .unsigned()
        .references('users.id');
    })

  // Then query the table...
  const insertedRows = await knex('users').insert({ user_name: 'Tim' })

  // ...and using the insert id, insert into the other table.
  await knex('accounts').insert({ account_name: 'knex', user_id: insertedRows[0] })

  // Query both of the rows.
  const selectedRows = await knex('users')
    .join('accounts', 'users.id', 'accounts.user_id')
    .select('users.user_name as user', 'accounts.account_name as account')

  // map over the results
  const enrichedRows = selectedRows.map(row => ({ ...row, active: true }))

  // Finally, add a catch statement
} catch(e) {
  console.error(e);
};

TypeScript example

import { Knex, knex } from 'knex'

interface User {
  id: number;
  age: number;
  name: string;
  active: boolean;
  departmentId: number;
}

const config: Knex.Config = {
  client: 'sqlite3',
  connection: {
    filename: './data.db',
  },
});

const knexInstance = knex(config);

try {
  const users = await knex<User>('users').select('id', 'age');
} catch (err) {
  // error handling
}

Usage as ESM module

If you are launching your Node application with --experimental-modules, knex.mjs should be picked up automatically and named ESM import should work out-of-the-box. Otherwise, if you want to use named imports, you'll have to import knex like this:

import { knex } from 'knex/knex.mjs'

You can also just do the default import:

import knex from 'knex'

If you are not using TypeScript and would like the IntelliSense of your IDE to work correctly, it is recommended to set the type explicitly:

/**
 * @type {Knex}
 */
const database = knex({
    client: 'mysql',
    connection: {
      host : '127.0.0.1',
      user : 'your_database_user',
      password : 'your_database_password',
      database : 'myapp_test'
    }
  });
database.migrate.latest();