ForeignKey( 'pethandler.handler_id'), nullable = False) # create a handler id column establishing a relationship with the foreign key class table handler_id = db. # create pet id, name, category column pet_id = db. # create pet category table class PetCategory(db. Simply, the pet handler is the attribute having multiple relationships with the pets, therefore the pets will have a column consisting of a ForeignKey() to the pet handler’s unique identify key which is the pet handler’s id handler_id. We create a column containing a ForeignKey() in the PetCategory class.

The representation of this relationship in our model is by following this process: One-to-many relationshipįrom our pet management system as an analogy, an example of a one-to-many relationship is analyzed between a pet handler and a pet in the PetCategory, such that a pet handler can be assigned to multiple (many) pets to care for. You might not understand the implementation of the code above, but focus on the concept of database relationship, we will get to the point of the components of creating a database. # create comment content column comment_content = db. # create comment id column comment_id = db. # create pet category column pet_category = db. # pet category class class PetCategory(db. # create handler name column handler_name = db. # create handler id column handler_id = db. The application will consist of the following models: PetHandler, PetCategory, and PetComment as shown below: In our understanding of the various database relationships, consider the creation of a Pet management system. In the process of working with databases, the following are the two types of relationship that you would frequently interact with when working with tables: To do this, we first need to understand the basic database relationship and how they are being initialized in our models. For example, a user might have a specific ID, such that this specific ID also refers back to the user, but how do we tell the database about the existence of this symbiotic relationship? In the process of creating models, we find that some models do have some relationship to one another or with other data. However, to solve this problem we have to start working with database models for the application. But we can’t add data to this database because it contains no tables for storing the registration details. # create an instance of the database module db = SQLAlchemy(app)īy following the process above, we have our database initialized and ready to work with. We proceed to clone the starter pack file from this Github repository. To make the process easier, we will clone an existing Flask web application used in our previous tutorial which contains a registration form with all the routes setup. Adding user data to registration databaseīefore we can work with the SQLAlchemy library, we need to have a Flask application running.Storing user registration data with SQLAlchemy.Intermediate knowledge with the use of terminal.

Understanding of Flask views and templates.

Understanding of Object-Oriented Programming concepts with Python.

Basic usage and implementation of a Flask web app.

The prerequisites for this article includes understanding of the following concepts: An ORM makes writing SQL queries easier for a programmer, because it enables us to write queries in an object-oriented language, and then ORM automatically translates it to SQL and retrieves the result as an object. In Flask web applications, to manipulate databases, we can use SQL and Object Relational Mapping (ORM). Therefore, the information supplied by the user has to be stored in a database so it can be accessed later. If the user can’t send or receive data from your web application, then it’s not providing value in its usage. Simultaneously, the user also requests information from where they are stored.ĭata and information are facets that make web applications valuable. Throughout the life-cycle of a web application, the user sends bits of data that are needed to be stored for future reference. Databases are integral components of building web applications.

Flask sqlite setup