Sequel is a lightweight, thread-safe database toolkit and ORM for Ruby.
Connecting to Databases
require 'sequel'
# SQLite in-memory or file
DB = Sequel.sqlite('database.db')
# PostgreSQL / MySQL
DB = Sequel.connect('postgres://user:password@localhost/mydb', max_connections: 10)
Datasets & Queries
Sequel expressions are chainable and lazily evaluated:
items = DB[:items] # Represents dataset
# Select, Where, Order
items.where(category: 'tools').order(:price).limit(10).all
# Complex filters
items.where{ price > 100 }
items.exclude(status: 'archived')
# Insert & Update
items.insert(name: 'Hammer', price: 15.99)
items.where(id: 1).update(price: 19.99)
# Delete
items.where(id: 1).delete
Sequel Models
class User < Sequel::Model
plugin :validation_helpers
plugin :timestamps
one_to_many :posts
def validate
super
validates_presence [:name, :email]
validates_unique :email
end
end
user = User.create(name: 'Alice', email: '[email protected]')
Database Transactions
DB.transaction do
account_a.update(balance: account_a.balance - 100)
account_b.update(balance: account_b.balance + 100)
end