Knex.js Cheat Sheet

SQL query builder for Node.js - queries, schema, migrations, and transactions.

Installation & Setup

Install Knex.js and configure database connection

# Install knex and your database driver
npm install knex --save

# Database drivers (choose one)
npm install pg          # PostgreSQL
npm install mysql2      # MySQL
npm install sqlite3     # SQLite
npm install tedious     # MSSQL

Package installation

const knex = require('knex')({
  client: 'mysql2',
  connection: {
    host: '127.0.0.1',
    port: 3306,
    user: 'your_database_user',
    password: 'your_database_password',
    database: 'myapp_test'
  },
  pool: { min: 0, max: 7 }
});

Basic configuration

// Connection string
const knex = require('knex')({
  client: 'pg',
  connection: process.env.DATABASE_URL,
  searchPath: ['knex', 'public']
});

// SQLite in-memory
const knex = require('knex')({
  client: 'sqlite3',
  connection: { filename: ':memory:' },
  useNullAsDefault: true
});

Alternative connection methods

Basic Queries

Select, insert, update, and delete operations

// Select all
knex('users').select('*')
// SELECT * FROM users

// Select specific columns
knex('users').select('id', 'name', 'email')
// SELECT id, name, email FROM users

// Select with alias
knex('users').select('id', 'name as full_name')
// SELECT id, name as full_name FROM users

// First result
knex('users').first('*')
// SELECT * FROM users LIMIT 1

SELECT queries

// Insert single row
knex('users').insert({ name: 'John', email: 'john@example.com' })

// Insert multiple rows
knex('users').insert([
  { name: 'John', email: 'john@example.com' },
  { name: 'Jane', email: 'jane@example.com' }
])

// Insert with returning (PostgreSQL)
knex('users')
  .insert({ name: 'John', email: 'john@example.com' })
  .returning('id')

INSERT queries

// Update all rows
knex('users').update({ status: 'active' })

// Update specific rows
knex('users')
  .where('id', 1)
  .update({ name: 'John Updated' })

// Update with returning
knex('users')
  .where('id', 1)
  .update({ name: 'John' })
  .returning('*')

UPDATE queries

// Delete all rows
knex('users').del()

// Delete specific rows
knex('users').where('id', 1).del()

// Delete with returning
knex('users')
  .where('id', 1)
  .del()
  .returning('*')

DELETE queries

WHERE Clauses

Filtering data with various conditions

// Simple where
knex('users').where('id', 1)
knex('users').where({ id: 1, status: 'active' })

// Where with operator
knex('users').where('age', '>', 18)
knex('users').where('created_at', '<=', '2024-01-01')

// Multiple conditions (AND)
knex('users')
  .where('status', 'active')
  .where('age', '>', 18)

// OR conditions
knex('users')
  .where('status', 'active')
  .orWhere('role', 'admin')

Basic WHERE

// Where IN
knex('users').whereIn('id', [1, 2, 3])

// Where NOT IN
knex('users').whereNotIn('status', ['banned', 'deleted'])

// Where NULL
knex('users').whereNull('deleted_at')

// Where NOT NULL
knex('users').whereNotNull('email')

// Where BETWEEN
knex('users').whereBetween('age', [18, 65])

// Where NOT BETWEEN
knex('users').whereNotBetween('age', [0, 18])

Advanced WHERE

// Complex nested conditions
knex('users')
  .where('status', 'active')
  .where(function() {
    this.where('role', 'admin')
      .orWhere('role', 'moderator')
  })
// WHERE status = 'active' AND (role = 'admin' OR role = 'moderator')

// Where EXISTS
knex('users')
  .whereExists(function() {
    this.select('*')
      .from('orders')
      .whereRaw('orders.user_id = users.id')
  })

// Raw WHERE
knex('users').whereRaw('age > ?', [18])

Complex WHERE

Joins

Combining data from multiple tables

// INNER JOIN
knex('users')
  .join('orders', 'users.id', '=', 'orders.user_id')
  .select('users.name', 'orders.total')

// LEFT JOIN
knex('users')
  .leftJoin('orders', 'users.id', 'orders.user_id')
  .select('users.name', 'orders.total')

// RIGHT JOIN
knex('users')
  .rightJoin('orders', 'users.id', 'orders.user_id')

// FULL OUTER JOIN
knex('users')
  .fullOuterJoin('orders', 'users.id', 'orders.user_id')

Basic joins

// Join with multiple conditions
knex('users')
  .join('orders', function() {
    this.on('users.id', '=', 'orders.user_id')
      .andOn('orders.status', '=', knex.raw('?', ['completed']))
  })

// Join with OR condition
knex('users')
  .join('orders', function() {
    this.on('users.id', '=', 'orders.user_id')
      .orOn('users.email', '=', 'orders.email')
  })

// Cross join
knex('users').crossJoin('roles')

Advanced joins

Aggregations & Grouping

Aggregate functions and GROUP BY operations

// Count
knex('users').count('id as total')

// Count distinct
knex('users').countDistinct('email')

// Sum
knex('orders').sum('total as revenue')

// Average
knex('orders').avg('total as average_order')

// Min and Max
knex('orders').min('total as min_order')
knex('orders').max('total as max_order')

Aggregate functions

// Group by
knex('orders')
  .select('user_id')
  .count('id as order_count')
  .groupBy('user_id')

// Group by multiple columns
knex('orders')
  .select('user_id', 'status')
  .sum('total as revenue')
  .groupBy('user_id', 'status')

// Having clause
knex('orders')
  .select('user_id')
  .count('id as order_count')
  .groupBy('user_id')
  .having('order_count', '>', 5)

// Having with raw
knex('orders')
  .select('user_id')
  .sum('total as revenue')
  .groupBy('user_id')
  .havingRaw('SUM(total) > ?', [1000])

GROUP BY and HAVING

Ordering & Limiting

Sort and paginate query results

// Order by ascending
knex('users').orderBy('name')
knex('users').orderBy('name', 'asc')

// Order by descending
knex('users').orderBy('created_at', 'desc')

// Multiple order columns
knex('users')
  .orderBy('status', 'asc')
  .orderBy('created_at', 'desc')

// Order by array
knex('users').orderBy([
  { column: 'status', order: 'asc' },
  { column: 'name', order: 'desc' }
])

// Order by raw
knex('users').orderByRaw('age DESC NULLS LAST')

Ordering

// Limit
knex('users').limit(10)

// Offset
knex('users').offset(20)

// Pagination
knex('users')
  .limit(10)
  .offset(20)

// Distinct
knex('users').distinct('email')

// Distinct on multiple columns
knex('users').distinct('email', 'status')

Limiting and pagination

Schema - Creating Tables

Define and create database tables

// Create table
knex.schema.createTable('users', function(table) {
  table.increments('id').primary();
  table.string('name', 100).notNullable();
  table.string('email', 255).unique().notNullable();
  table.integer('age');
  table.boolean('is_active').defaultTo(true);
  table.timestamps(true, true);
});

// Create table if not exists
knex.schema.createTableIfNotExists('users', function(table) {
  table.increments('id');
  table.string('email').unique();
});

Basic table creation

// Common column types
table.increments('id')              // Auto-incrementing ID
table.integer('votes')              // Integer
table.bigInteger('big_votes')       // Big integer
table.text('description')           // Text
table.string('name', 255)           // String with length
table.float('amount')               // Float
table.decimal('price', 8, 2)        // Decimal(8,2)
table.boolean('is_admin')           // Boolean
table.date('birth_date')            // Date
table.datetime('created_at')        // Datetime
table.time('alarm_time')            // Time
table.timestamp('updated_at')       // Timestamp
table.json('metadata')              // JSON
table.jsonb('data')                 // JSONB (PostgreSQL)
table.uuid('id')                    // UUID
table.enum('status', ['active', 'inactive'])  // Enum

Column types

// Column modifiers
table.string('email')
  .notNullable()           // NOT NULL
  .unique()                // UNIQUE
  .defaultTo('default')    // DEFAULT value
  .unsigned()              // UNSIGNED (for numbers)
  .index()                 // Add index
  .comment('Email address') // Add comment

// Foreign keys
table.integer('user_id')
  .unsigned()
  .notNullable()
  .references('id')
  .inTable('users')
  .onDelete('CASCADE')
  .onUpdate('CASCADE');

// Timestamps helpers
table.timestamps(true, true)  // created_at, updated_at
table.timestamp('created_at').defaultTo(knex.fn.now())

Column modifiers and constraints

Schema - Altering Tables

Modify existing table structures

// Add column
knex.schema.table('users', function(table) {
  table.string('phone', 20);
});

// Add multiple columns
knex.schema.table('users', function(table) {
  table.string('phone', 20);
  table.string('address', 255);
  table.integer('zip_code');
});

// Alter column
knex.schema.alterTable('users', function(table) {
  table.string('email', 500).alter();
});

// Rename column
knex.schema.table('users', function(table) {
  table.renameColumn('name', 'full_name');
});

Modifying tables

// Drop column
knex.schema.table('users', function(table) {
  table.dropColumn('phone');
});

// Drop multiple columns
knex.schema.table('users', function(table) {
  table.dropColumns('phone', 'address');
});

// Drop table
knex.schema.dropTable('users');

// Drop table if exists
knex.schema.dropTableIfExists('users');

// Rename table
knex.schema.renameTable('users', 'customers');

Dropping and renaming

// Check if table exists
knex.schema.hasTable('users')
  .then(exists => {
    if (!exists) {
      return knex.schema.createTable('users', table => {
        table.increments('id');
      });
    }
  });

// Check if column exists
knex.schema.hasColumn('users', 'email')
  .then(exists => {
    if (!exists) {
      return knex.schema.table('users', table => {
        table.string('email');
      });
    }
  });

Schema checks

Schema - Indexes & Foreign Keys

Create and manage database indexes and relationships

// Create index
knex.schema.table('users', function(table) {
  table.index('email');
});

// Create named index
knex.schema.table('users', function(table) {
  table.index('email', 'idx_users_email');
});

// Composite index
knex.schema.table('users', function(table) {
  table.index(['status', 'created_at'], 'idx_status_created');
});

// Unique index
knex.schema.table('users', function(table) {
  table.unique('email');
});

// Drop index
knex.schema.table('users', function(table) {
  table.dropIndex('email');
  table.dropIndex([], 'idx_users_email'); // by name
});

Indexes

// Add foreign key
knex.schema.table('orders', function(table) {
  table.foreign('user_id')
    .references('id')
    .inTable('users');
});

// Foreign key with actions
knex.schema.table('orders', function(table) {
  table.foreign('user_id')
    .references('id')
    .inTable('users')
    .onDelete('CASCADE')
    .onUpdate('RESTRICT');
});

// Named foreign key
knex.schema.table('orders', function(table) {
  table.foreign('user_id', 'fk_orders_user')
    .references('users.id');
});

// Drop foreign key
knex.schema.table('orders', function(table) {
  table.dropForeign('user_id');
  table.dropForeign([], 'fk_orders_user'); // by name
});

Foreign keys

Transactions

Execute multiple queries atomically

// Basic transaction
knex.transaction(async (trx) => {
  await trx('users').insert({ name: 'John' });
  await trx('orders').insert({ user_id: 1, total: 100 });
})
.then(() => console.log('Transaction committed'))
.catch((err) => console.error('Transaction failed:', err));

// Transaction with return value
const userId = await knex.transaction(async (trx) => {
  const [id] = await trx('users')
    .insert({ name: 'John' })
    .returning('id');
  
  await trx('profiles')
    .insert({ user_id: id, bio: 'Hello' });
  
  return id;
});

Basic transactions

// Manual transaction control
const trx = await knex.transaction();

try {
  await trx('users').insert({ name: 'John' });
  await trx('orders').insert({ user_id: 1, total: 100 });
  await trx.commit();
} catch (err) {
  await trx.rollback();
  throw err;
}

// Transaction with savepoints
knex.transaction(async (trx) => {
  await trx('users').insert({ name: 'John' });
  
  const savepoint = await trx.savepoint();
  try {
    await trx('orders').insert({ user_id: 1, total: 100 });
    await savepoint.release();
  } catch (err) {
    await savepoint.rollback();
  }
});

Advanced transaction control

Raw Queries

Execute raw SQL when needed

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

// Raw query with named bindings
knex.raw('SELECT * FROM users WHERE id = :userId', {
  userId: 1
})

// Raw in select
knex('users')
  .select(knex.raw('COUNT(*) as total'))
  .where('status', 'active')

// Raw in where
knex('users')
  .whereRaw('age > ?', [18])
  .orWhereRaw('status = ?', ['admin'])

Basic raw queries

// Raw update
knex('users')
  .update({
    updated_at: knex.raw('NOW()'),
    views: knex.raw('views + 1')
  })
  .where('id', 1)

// Raw insert
knex('users').insert({
  name: 'John',
  created_at: knex.raw('CURRENT_TIMESTAMP')
})

// Using knex.ref for column references
knex('users')
  .where('created_at', '>', knex.ref('updated_at'))

Raw in queries

Migrations

Version control for database schema

# Create migration
npx knex migrate:make create_users_table

# Run migrations
npx knex migrate:latest

# Rollback last batch
npx knex migrate:rollback

# Rollback all migrations
npx knex migrate:rollback --all

# Check migration status
npx knex migrate:status

# Run specific migration
npx knex migrate:up 001_create_users.js

Migration commands

// Migration file structure
exports.up = function(knex) {
  return knex.schema.createTable('users', function(table) {
    table.increments('id').primary();
    table.string('name', 100).notNullable();
    table.string('email', 255).unique().notNullable();
    table.timestamp('created_at').defaultTo(knex.fn.now());
  });
};

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

Migration file example

// Migration with multiple operations
exports.up = async function(knex) {
  // Create users table
  await knex.schema.createTable('users', table => {
    table.increments('id');
    table.string('email').unique();
  });
  
  // Create orders table
  await knex.schema.createTable('orders', table => {
    table.increments('id');
    table.integer('user_id').unsigned();
    table.foreign('user_id').references('users.id');
  });
  
  // Seed initial data
  await knex('users').insert([
    { email: 'admin@example.com' }
  ]);
};

exports.down = async function(knex) {
  await knex.schema.dropTable('orders');
  await knex.schema.dropTable('users');
};

Complex migration

Seeds

Populate database with test data

# Create seed file
npx knex seed:make 01_users

# Run all seeds
npx knex seed:run

# Run specific seed
npx knex seed:run --specific=01_users.js

Seed commands

// Basic seed file
exports.seed = async function(knex) {
  // Delete existing entries
  await knex('users').del();
  
  // Insert seed data
  await knex('users').insert([
    { name: 'John Doe', email: 'john@example.com' },
    { name: 'Jane Smith', email: 'jane@example.com' },
    { name: 'Bob Johnson', email: 'bob@example.com' }
  ]);
};

Basic seed

// Seed with relations
exports.seed = async function(knex) {
  // Clear tables in correct order
  await knex('orders').del();
  await knex('users').del();
  
  // Insert users and get IDs
  const [userId1] = await knex('users')
    .insert({ name: 'John', email: 'john@example.com' })
    .returning('id');
  
  const [userId2] = await knex('users')
    .insert({ name: 'Jane', email: 'jane@example.com' })
    .returning('id');
  
  // Insert related orders
  await knex('orders').insert([
    { user_id: userId1, total: 100.50 },
    { user_id: userId1, total: 75.25 },
    { user_id: userId2, total: 200.00 }
  ]);
};

Seed with relationships

TypeScript Support

Type-safe queries with TypeScript

// Define table types
interface User {
  id: number;
  name: string;
  email: string;
  created_at: string;
  updated_at: string;
}

interface UserInsert {
  name: string;
  email: string;
}

interface UserUpdate {
  name?: string;
  email?: string;
  updated_at?: string;
}

Type definitions

// Augment Knex types
import { Knex } from 'knex';

declare module 'knex/types/tables' {
  interface Tables {
    users: User;
    users_composite: Knex.CompositeTableType<
      User,
      UserInsert,
      UserUpdate
    >;
  }
}

// Type-safe queries
const users = await knex('users').select('*');
// users is typed as User[]

const newUser = await knex('users_composite')
  .insert({ name: 'John', email: 'john@example.com' })
  .returning('*');

Type augmentation

// Generic query types
const getUserById = async (id: number): Promise<User | undefined> => {
  return knex<User>('users')
    .where({ id })
    .first();
};

const createUser = async (data: UserInsert): Promise<User> => {
  const [user] = await knex<User>('users')
    .insert(data)
    .returning('*');
  return user;
};

const updateUser = async (
  id: number,
  data: UserUpdate
): Promise<User | undefined> => {
  const [user] = await knex<User>('users')
    .where({ id })
    .update(data)
    .returning('*');
  return user;
};

Typed query functions

Advanced Features

Advanced Knex.js capabilities

// Upsert (insert or update)
knex('users')
  .insert({ id: 1, name: 'John', email: 'john@example.com' })
  .onConflict('id')
  .merge()

// Upsert with specific columns
knex('users')
  .insert({ id: 1, name: 'John', email: 'john@example.com' })
  .onConflict('email')
  .merge(['name'])

// Insert ignore (MySQL)
knex('users')
  .insert({ email: 'john@example.com' })
  .onConflict('email')
  .ignore()

Upsert operations

// WITH (Common Table Expressions)
knex.with('active_users', (qb) => {
  qb.select('*').from('users').where('status', 'active');
})
.select('*')
.from('active_users')
.where('age', '>', 18);

// Recursive CTE
knex.withRecursive('tree', (qb) => {
  qb.select('*').from('categories').where('parent_id', null)
    .union((qb2) => {
      qb2.select('c.*')
        .from('categories as c')
        .join('tree as t', 'c.parent_id', 't.id');
    });
})
.select('*').from('tree');

Common Table Expressions

// Subqueries
knex('users')
  .whereIn('id', function() {
    this.select('user_id').from('orders').where('total', '>', 100);
  })

// Subquery in select
knex('users')
  .select('name')
  .select(
    knex('orders')
      .count('*')
      .where('orders.user_id', knex.raw('??', ['users.id']))
      .as('order_count')
  )

// Subquery in from
knex
  .select('*')
  .from(
    knex('users')
      .where('status', 'active')
      .as('active_users')
  )

Subqueries

// Window functions
knex('orders')
  .select('*')
  .select(
    knex.raw('ROW_NUMBER() OVER (PARTITION BY user_id ORDER BY created_at DESC) as row_num')
  )

// JSON operations (PostgreSQL)
knex('users')
  .select('name')
  .select(knex.raw("metadata->>'age' as age"))
  .where(knex.raw("metadata->>'city'"), 'New York')

// Array operations (PostgreSQL)
knex('users')
  .whereRaw('? = ANY(tags)', ['javascript'])

Advanced SQL features

Connection & Pool Management

Manage database connections and pool

// Configure connection pool
const knex = require('knex')({
  client: 'pg',
  connection: {
    host: '127.0.0.1',
    user: 'user',
    password: 'password',
    database: 'myapp'
  },
  pool: {
    min: 2,
    max: 10,
    acquireTimeoutMillis: 30000,
    idleTimeoutMillis: 30000
  }
});

// Destroy connection pool
await knex.destroy();

// Re-initialize
knex.initialize();

Pool configuration

// Connection afterCreate hook
const knex = require('knex')({
  client: 'pg',
  connection: { /* ... */ },
  pool: {
    afterCreate: function(conn, done) {
      conn.query('SET timezone="UTC";', function(err) {
        done(err, conn);
      });
    }
  }
});

// Dynamic connection
const knex = require('knex')({
  client: 'mysql',
  connection: async () => {
    const token = await getAuthToken();
    return {
      host: 'localhost',
      user: 'user',
      password: token,
      database: 'myapp'
    };
  }
});

Connection hooks

// Debugging queries
const knex = require('knex')({
  client: 'pg',
  connection: { /* ... */ },
  debug: true  // Log all queries
});

// Debug specific query
knex('users')
  .select('*')
  .debug()
  .then(rows => console.log(rows));

// Get SQL without executing
const sql = knex('users')
  .where('id', 1)
  .toSQL();
console.log(sql.sql);      // SQL string
console.log(sql.bindings); // Parameters

Debugging

Knex.js Cheat Sheet