Database Operations Deep Dive

Introduction

SQLAlchemy provides a Pythonic way to interact with databases using ORM and SQL expression.

Engine and Connection

from sqlalchemy import create_engine

engine = create_engine("sqlite:///mydb.sqlite")
connection = engine.connect()

# Execute raw SQL
result = connection.execute("SELECT * FROM users")

ORM Basics

from sqlalchemy import Column, Integer, String
from sqlalchemy.orm import declarative_base

Base = declarative_base()

class User(Base):
    __tablename__ = "users"
    
    id = Column(Integer, primary_key=True)
    name = Column(String(100))
    email = Column(String(100))

# Create tables
Base.metadata.create_all(engine)

Session and CRUD

from sqlalchemy.orm import sessionmaker

Session = sessionmaker(bind=engine)
session = Session()

# Create
user = User(name="Alice", email="alice@email.com")
session.add(user)
session.commit()

# Read
user = session.query(User).filter_by(name="Alice").first()

# Update
user.email = "new@email.com"
session.commit()

# Delete
session.delete(user)
session.commit()

Practice Problems

1. Create tables with SQLAlchemy ORM
2. Perform CRUD operations
3. Query with filters
4. Update multiple records
5. Use relationships between models