Sequel è un toolkit per database leggero e thread-safe nonché un ORM completo per Ruby.
Connessione ai database
require 'sequel'
# SQLite in memoria o su file
DB = Sequel.sqlite('database.db')
# PostgreSQL / MySQL
DB = Sequel.connect('postgres://user:password@localhost/mydb', max_connections: 10)
Dataset e Query
Le espressioni Sequel sono concatenabili e valutate in modo lazy:
items = DB[:items] # Rappresenta il dataset
# Select, Where, Order
items.where(category: 'tools').order(:price).limit(10).all
# Filtri complessi
items.where{ price > 100 }
items.exclude(status: 'archived')
# Inserimento e aggiornamento
items.insert(name: 'Hammer', price: 15.99)
items.where(id: 1).update(price: 19.99)
# Eliminazione
items.where(id: 1).delete
Modelli Sequel
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]')
Transazioni di database
DB.transaction do
account_a.update(balance: account_a.balance - 100)
account_b.update(balance: account_b.balance + 100)
end