CRUD Operations in SQLAlchemy

 

What is CRUD?

Operation       Meaning
Create            Insert data
Read            Fetch data
Update            Modify data
Delete            Remove data


CREATE (Insert Data)

new_user = User(name="Alice", email="alice@example.com")

session.add(new_user)
session.commit()

READ (Query Data)

Get All Users

users = session.query(User).all()

for user in users:
    print(user.name, user.email)

Filter Data

user = session.query(User).filter_by(name="Alice").first()
print(user.email)

UPDATE Data

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

user.email = "alice_new@example.com"
session.commit()

DELETE Data

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

session.delete(user)
session.commit()


Transaction Handling (Very Important)
try:
    session.add(User(name="Bob", email="bob@example.com"))
    session.commit()
except:
    session.rollback()


Bulk Insert
users = [
    User(name="A", email="a@test.com"),
    User(name="B", email="b@test.com"),
]

session.bulk_save_objects(users)
session.commit()

Real-World Example
API Endpoint (FastAPI Style)
@app.post("/users")
def create_user(name: str, email: str):
    user = User(name=name, email=email)
    session.add(user)
    session.commit()
    return {"message": "User created"}
Common Mistakes
  • Forgetting commit()

  • Using .all() when only one record needed

  • Not handling exceptions

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