CRUD Operations
CRUD stands for Create, Read, Update, Delete – the four basic operations on data. Flask‑SQLAlchemy makes these operations simple.
Create (Insert)
new_user = User(username='alice', email='alice@example.com', password='secret')
db.session.add(new_user)
db.session.commit()Read (Query)
# Get all users
users = User.query.all()
# Get first user
user = User.query.first()
# Filter by username
user = User.query.filter_by(username='alice').first()
# Get user by primary key
user = User.query.get(1)Update
user = User.query.get(1)
user.username = 'alice_new'
db.session.commit()Delete
user = User.query.get(1)
db.session.delete(user)
db.session.commit()Using Queries in Routes
@app.route('/users')
def list_users():
users = User.query.all()
return render_template('users.html', users=users)Two Minute Drill
- Add to session: `db.session.add(object)` → commit.
- Query: `Model.query.all()`, `filter_by()`, `get(id)`.
- Update: modify object attributes → commit.
- Delete: `db.session.delete(object)` → commit.
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