**Course Title:** PySide6 Application Development **Section Title:** Integrating Databases with PySide6 **Topic:** Using QSqlDatabase and QSqlQuery for database operations ### Introduction In the previous topic, we introduced SQL databases and their role in PySide6 application development. In this topic, we'll dive deeper into the QSqlDatabase and QSqlQuery classes, which provide a convenient and efficient way to interact with various databases using SQL. We'll explore how to establish connections, execute queries, and manipulate data using these classes. ### QSqlDatabase QSqlDatabase is a class that provides a connection to a database. It's a high-level interface that allows you to manage database connections, execute queries, and retrieve results. To use QSqlDatabase, you need to: 1. **Add** the **qt_sql** module to your PySide6 project. 2. **Import** the `QSqlDatabase` class from `PySide6.QtSql`. Here's an example: ```python from PySide6.QtSql import QSqlDatabase, QSqlQuery # Create a database connection db = QSqlDatabase.addDatabase('QMYSQL') db.setHostName('localhost') db.setPort(3306) db.setDatabaseName('mydatabase') db.setUserName('myusername') db.setPassword('mypassword') # Open the database connection if db.open(): print("Database connection established") else: print("Error:", db.lastError().text()) ``` In this example, we create a `QSqlDatabase` object and set its properties to connect to a MySQL database. We then open the connection using the `open()` method. If the connection is successful, we print a success message; otherwise, we print an error message. ### QSqlQuery QSqlQuery is a class that allows you to execute SQL queries and retrieve results. You can use it to execute queries, insert, update, or delete data. Here's an example: ```python query = QSqlQuery(db) # Execute a query query.exec_('SELECT * FROM mytable') # Fetch results while query.next(): print(query.value(0), query.value(1)) ``` In this example, we create a `QSqlQuery` object and execute a `SELECT * FROM mytable` query using the `exec_()` method. We then fetch the results using the `next()` method and print the values of each row. ### Binding Values To avoid SQL injection attacks, it's a good practice to bind values to your queries instead of concatenating them. You can use the `prepare()` and `bindValue()` methods to achieve this. Here's an example: ```python query = QSqlQuery(db) # Prepare a query with a parameter query.prepare_('SELECT * FROM mytable WHERE id = ?') # Bind a value to the parameter query.bindValue(0, 1) # id = 1 # Execute the query query.exec_() # Fetch results while query.next(): print(query.value(0), query.value(1)) ``` In this example, we prepare a query with a parameter (`?`) and bind a value (`1`) to it using the `bindValue()` method. This way, we avoid concatenating values and prevent SQL injection attacks. ### Conclusion In this topic, we covered the basics of using `QSqlDatabase` and `QSqlQuery` for database operations in PySide6. We learned how to establish connections, execute queries, and bind values to prevent SQL injection attacks. Remember to always follow best practices when interacting with databases, such as using prepared statements and binding values. ### What's Next? In the next topic, we'll learn how to perform CRUD (Create, Read, Update, Delete) operations using `QSqlDatabase` and `QSqlQuery`. You'll get hands-on experience with practical examples and exercises. **Leave a comment** below if you have any questions or need help with any of the concepts covered in this topic. **External Resources:** * [PySide6 documentation](https://www.riverbankcomputing.com/static/Docs/PySide6/qtforpython/index.html) * [QSqlDatabase documentation](https://doc.qt.io/qtforpython-5/PySide6/QtSql/QSqlDatabase.html) * [QSqlQuery documentation](https://doc.qt.io/qtforpython-5/PySide6/QtSql/QSqlQuery.html) Please leave a comment below if you have any questions or need help with any of the concepts covered in this topic.