Connecting Flask to a Database: Basic CRUD Operations

Learning Objectives Define the four CRUD operations (Create, Read, Update, Delete) and their purpose in web applications. Set up a simple SQLite database and connect it to a Flask application using Flask-SQLAlchemy. Implement the 'Create' operation by processing an HTML form to add new data to the database. Implement the 'Read' operation by querying the database and displaying all records on a web page. Implement the 'Update' operation to edit an existing database record through a web interface. Implement the 'Delete' operation to remove a specific record from the database based on user input. Ever wonder how Instagram saves your photos or how your favorite game saves your high score? 🏆 It's all about talking to a database! In t...

TermDefinitionExample CRUDAn acronym for the four basic functions of persistent storage: Create, Read, Update, and Delete. These are the fundamental operations for interacting with any database.In a contacts app: Creating a new contact, Reading the list of all contacts, Updating a phone number, and Deleting a contact. DatabaseAn organized collection of structured information, or data, typically stored electronically in a computer system, allowing for efficient retrieval and management.A spreadsheet file containing a table of student names, IDs, and grades. Flask-SQLAlchemyA Flask extension that adds support for SQLAlchemy, an Object-Relational Mapper (ORM). It lets us interact with our database using Python objects and methods instead of writing raw SQL commands.Instead of writing `INSERT...

Defining a Database Model class ModelName(db.Model): id = db.Column(db.Integer, primary_key=True) name = db.Column(db.String(100), nullable=False) Use this class structure to define a table in your database. Each class variable using `db.Column` becomes a column in the table, with a specified data type (like Integer or String). Creating and Saving a New Record (Create) new_record = ModelName(name='value') db.session.add(new_record) db.session.commit() To add a new row, first create an instance of your model class with the data. Then, use `db.session.add()` to stage it for saving, and `db.session.commit()` to write it permanently to the database. Querying for Records (Read) all_records = ModelName.query.all() single_record = ModelName.query.get(primary_key...