Could you explain the principle and the operation of registry objects in conjunction with databases, known as ORM?

Object-Relational Mapping (ORM) is a technology that allows working with a database through objects in code, hiding SQL details and data transformation.

How it works:

• Each database table maps to a class (object) in the programming language.
• Rows correspond to instances of these classes.
• Table columns are object attributes.

Objects-registries (entity objects) represent database records and contain methods for reading, modifying, and saving data.

Advantages:

• Simplifies data handling — developers work with objects, not SQL.
• Automatic management of relationships between tables.
• Caching and query optimization.

Example in Python with SQLAlchemy:

from sqlalchemy import Column, Integer, String, create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Base = declarative_base()

class User(Base):
    __tablename__ = 'users'
    id = Column(Integer, primary_key=True)
    name = Column(String)

engine = create_engine('sqlite:///:memory:')
Base.metadata.create_all(engine)
Session = sessionmaker(bind=engine)
session = Session()

# Create a new user
new_user = User(name='Alice')
session.add(new_user)
session.commit()

# Query user
user = session.query(User).filter_by(name='Alice').first()
print(user.name)  # Alice

Thus, ORM allows working with database as objects, increasing convenience and reducing errors.