Step 3: Proof of concept connecting to SQL using pyodbc

This sample proof of concept uses pyodbc to connect to a SQL database. This sample assumes that you're using the AdventureWorksLT sample database.

Notitie

This example should be considered a proof of concept only. The sample code is simplified for clarity, and does not necessarily represent best practices recommended by Microsoft.

Prerequisites

• Python 3
  • If you don't already have Python, install the Python runtime and Python Package Index (PyPI) package manager from python.org.
  • Prefer to not use your own environment? Open as a devcontainer using GitHub Codespaces.
    • .
• pyodbc package from PyPI.
• Install the Microsoft ODBC Driver 18 for SQL Server
• A SQL database and credentials.

Connect and query data

Connect to a database using your credentials.

1. Create a new file named app.py.

2. Add a module docstring.

   Python

   """
   Connects to a SQL database using pyodbc
   """
   

3. Import the pyodbc package.

   Python

   import pyodbc
   

4. Create variables for your connection credentials.

   Python

   SERVER = '<server-address>'
   DATABASE = '<database-name>'
   USERNAME = '<username>'
   PASSWORD = '<password>'
   

5. Create a connection string variable using string interpolation.

   Python

   connectionString = f'DRIVER={{ODBC Driver 18 for SQL Server}};SERVER={SERVER};DATABASE={DATABASE};UID={USERNAME};PWD={PASSWORD}'
   

6. Use the pyodbc.connect function to connect to a SQL database.

   Python

   conn = pyodbc.connect(connectionString) 
   

Execute a query

Use a SQL query string to execute a query and parse the results.

1. Create a variable for the SQL query string.

   Python

   SQL_QUERY = """
   SELECT 
   TOP 5 c.CustomerID, 
   c.CompanyName, 
   COUNT(soh.SalesOrderID) AS OrderCount 
   FROM 
   SalesLT.Customer AS c 
   LEFT OUTER JOIN SalesLT.SalesOrderHeader AS soh ON c.CustomerID = soh.CustomerID 
   GROUP BY 
   c.CustomerID, 
   c.CompanyName 
   ORDER BY 
   OrderCount DESC;
   """
   

2. Use cursor.execute to retrieve a result set from a query against the database.

   Python

   cursor = conn.cursor()
   cursor.execute(SQL_QUERY)
   

   Notitie

   This function essentially accepts any query and returns a result set, which can be iterated over with the use of cursor.fetchone().

3. Use cursor.fetchall with a foreach loop to get all the records from the database. Then print the records.

   Python

   records = cursor.fetchall()
   for r in records:
       print(f"{r.CustomerID}\t{r.OrderCount}\t{r.CompanyName}")
   

4. Save the app.py file.

5. Open a terminal and test the application.

   Bash

   python app.py
   

   Output

   29485   1       Professional Sales and Service
   29531   1       Remarkable Bike Store
   29546   1       Bulk Discount Store
   29568   1       Coalition Bike Company
   29584   1       Futuristic Bikes
   

Insert a row as a transaction

In this example, you execute an INSERT statement safely and pass parameters. Passing parameters as values protects your application from SQL injection attacks.

1. Import randrange from the random library.

   Python

   from random import randrange
   

2. Generate a random product number.

   Python

   productNumber = randrange(1000)
   

   Tip

   Generating a random product number here ensures that you can run this sample multiple times.

3. Create a SQL statement string.

   Python

   SQL_STATEMENT = """
   INSERT SalesLT.Product (
   Name, 
   ProductNumber, 
   StandardCost, 
   ListPrice, 
   SellStartDate
   ) OUTPUT INSERTED.ProductID 
   VALUES (?, ?, ?, ?, CURRENT_TIMESTAMP)
   """
   

4. Execute the statement using cursor.execute.

   Python

   cursor.execute(
       SQL_STATEMENT,
       f'Example Product {productNumber}', 
       f'EXAMPLE-{productNumber}', 
       100,
       200
   )
   

5. Fetch the first column of the single result using cursor.fetchval, print the result's unique identifier, and then commit the operation as a transaction using connection.commit.

   Python

   resultId = cursor.fetchval()
   print(f"Inserted Product ID : {resultId}")
   conn.commit()
   

   Tip

   Optionally, you can use connection.rollback to rollback the transaction.

6. Close the cursor and connection using cursor.close and connection.close.

   Python

   cursor.close()
   conn.close()
   

7. Save the app.py file and test the application again

   Bash

   python app.py
   

   Output

   Inserted Product ID : 1001
   

Next steps

Python Developer Center.