Inner Join between multiple tables in Flask using Python
To perform an inner join between multiple tables in Flask using Python, you can use the SQLAlchemy ORM (Object-Relational Mapping) library. Here's an example code snippet that shows how to do this:
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
app = Flask(__name__)
app.config['SQLALCHEMY_DATABASE_URI'] = 'postgresql://username:password@localhost/database_name'
db = SQLAlchemy(app)
class User(db.Model):
id = db.Column(db.Integer, primary_key=True)
name = db.Column(db.String(50))
email = db.Column(db.String(50))
class Order(db.Model):
id = db.Column(db.Integer, primary_key=True)
user_id = db.Column(db.Integer, db.ForeignKey('user.id'))
product = db.Column(db.String(50))
quantity = db.Column(db.Integer)
@app.route('/orders')
def orders():
orders = db.session.query(User, Order).join(Order, User.id == Order.user_id).all()
order_list = []
for user, order in orders:
order_list.append({'user': user.name, 'email': user.email, 'product': order.product, 'quantity': order.quantity})
return {'orders': order_list}
In this example, we have two models User and Order, with a one-to-many relationship between them. The User model has an id, name, and email column, while the Order model has an id, user_id, product, and quantity column. We want to fetch all the orders with the corresponding user information.
In the orders() function, we use the db.session.query() method to construct a SELECT statement that retrieves data from both the User and Order tables. We use the join() method to join the two tables on the user_id and id columns, respectively. The result is a list of tuples, where each tuple contains a User object and an Order object.
We then loop over the list of tuples and create a new list of dictionaries, where each dictionary contains the desired information about an order, including the user's name and email. Finally, we return the list of dictionaries as a JSON object.
Note that in this example, we assume that you have a PostgreSQL database running on your local machine, with a username and password that have access to a database called database_name. You will need to adjust the connection string accordingly to match your own database configuration.
Happy Learning!! Happy Coding!!
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