How to use SQLAlchemy ORM to access MySQL Data in Python

The rich ecosystem of Python modules lets you get to work quickly and integrate your systems effectively. With the CData Python Connector for MySQL and the SQLAlchemy toolkit, you can build MySQL-connected Python applications and scripts. This article shows how to use SQLAlchemy to connect to MySQL data to query, update, delete, and insert MySQL data.

With built-in optimized data processing, the CData Python Connector offers unmatched performance for interacting with live MySQL data in Python. When you issue complex SQL queries from MySQL, the CData Connector pushes supported SQL operations, like filters and aggregations, directly to MySQL and utilizes the embedded SQL engine to process unsupported operations client-side (often SQL functions and JOIN operations).

Connecting to MySQL Data

Connecting to MySQL data looks just like connecting to any relational data source. Create a connection string using the required connection properties. For this article, you will pass the connection string as a parameter to the create_engine function.

The CData Provider supports connecting to on-premises and cloud-hosted versions of MySQL such as Amazon RDS for MySQL, Google Cloud SQL for MySQL, Azure Database for MySQL, or Oracle MySQL HeatWave. The Server and Port properties must be set to a MySQL server. If IntegratedSecurity is set to false, then User and Password must be set to valid user credentials. Optionally, Database can be set to connect to a specific database. If not set, tables from all databases will be returned.

SSH Connectivity for MySQL

You can use SSH (Secure Shell) to authenticate with MySQL, whether the instance is hosted on-premises or in supported cloud environments. SSH authentication ensures that access is encrypted (as compared to direct network connections).

SSH Connections to MySQL in Password Auth Mode

To connect to MySQL via SSH in Password Auth mode, set the following connection properties:

• User: MySQL User name
• Password: MySQL Password
• Database: MySQL database name
• Server: MySQL Server name
• Port: MySQL port number like 3306
• UserSSH: "true"
• SSHAuthMode: "Password"
• SSHPort: SSH Port number
• SSHServer: SSH Server name
• SSHUser: SSH User name
• SSHPassword: SSH Password

SSH Connections to MySQL in Public Key Auth Mode

To connect to MySQL via SSH in Password Auth mode, set the following connection properties:

• User: MySQL User name
• Password: MySQL Password
• Database: MySQL database name
• Server: MySQL Server name
• Port: MySQL port number like 3306
• UserSSH: "true"
• SSHAuthMode: "Public_Key"
• SSHPort: SSH Port number
• SSHServer: SSH Server name
• SSHUser: SSH User name
• SSHClientCret: the path for the public key certificate file

Follow the procedure below to install SQLAlchemy and start accessing MySQL through Python objects.

Install Required Modules

Use the pip utility to install the SQLAlchemy toolkit and SQLAlchemy ORM package:

pip install sqlalchemy
pip install sqlalchemy.orm

Be sure to import the appropriate modules:

from sqlalchemy import create_engine, String, Column
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker

Model MySQL Data in Python

You can now connect with a connection string. Use the create_engine function to create an Engine for working with MySQL data.

NOTE: Users should URL encode the any connection string properties that include special characters. For more information, refer to the SQL Alchemy documentation.

engine = create_engine("mysql:///?User=myUser&Password=myPassword&Database=NorthWind&Server=myServer&Port=3306")

Declare a Mapping Class for MySQL Data

After establishing the connection, declare a mapping class for the table you wish to model in the ORM (in this article, we will model the Orders table). Use the sqlalchemy.ext.declarative.declarative_base function and create a new class with some or all of the fields (columns) defined.

base = declarative_base()
class Orders(base):
	__tablename__ = "Orders"
	ShipName = Column(String,primary_key=True)
	Freight = Column(String)
	...

Query MySQL Data

With the mapping class prepared, you can use a session object to query the data source. After binding the Engine to the session, provide the mapping class to the session query method.

Using the query Method

engine = create_engine("mysql:///?User=myUser&Password=myPassword&Database=NorthWind&Server=myServer&Port=3306")
factory = sessionmaker(bind=engine)
session = factory()
for instance in session.query(Orders).filter_by(ShipCountry="USA"):
	print("ShipName: ", instance.ShipName)
	print("Freight: ", instance.Freight)
	print("---------")

Alternatively, you can use the execute method with the appropriate table object. The code below works with an active session.

Using the execute Method

Orders_table = Orders.metadata.tables["Orders"]
for instance in session.execute(Orders_table.select().where(Orders_table.c.ShipCountry == "USA")):
	print("ShipName: ", instance.ShipName)
	print("Freight: ", instance.Freight)
	print("---------")

For examples of more complex querying, including JOINs, aggregations, limits, and more, refer to the Help documentation for the extension.

Insert MySQL Data

To insert MySQL data, define an instance of the mapped class and add it to the active session. Call the commit function on the session to push all added instances to MySQL.

new_rec = Orders(ShipName="placeholder", ShipCountry="USA")
session.add(new_rec)
session.commit()

Update MySQL Data

To update MySQL data, fetch the desired record(s) with a filter query. Then, modify the values of the fields and call the commit function on the session to push the modified record to MySQL.

updated_rec = session.query(Orders).filter_by(SOME_ID_COLUMN="SOME_ID_VALUE").first()
updated_rec.ShipCountry = "USA"
session.commit()

Delete MySQL Data

To delete MySQL data, fetch the desired record(s) with a filter query. Then delete the record with the active session and call the commit function on the session to perform the delete operation on the provided records (rows).

deleted_rec = session.query(Orders).filter_by(SOME_ID_COLUMN="SOME_ID_VALUE").first()
session.delete(deleted_rec)
session.commit()

Free Trial & More Information

Download a free, 30-day trial of the CData Python Connector for MySQL to start building Python apps and scripts with connectivity to MySQL data. Reach out to our Support Team if you have any questions.