**Course Title:** Qt 6 Application Development with C++ **Section Title:** Integrating Databases with Qt **Topic:** Displaying database data using QTableView and QSqlTableModel In the previous topics, we've learned the basics of database integration in Qt using QSqlDatabase and QSqlQuery. Now, we'll explore how to display database data using QTableView and QSqlTableModel. This topic will show you how to create a simple database-driven application with a user-friendly interface. **QSqlTableModel** QSqlTableModel is a high-level interface for accessing database data in Qt. It provides a model that can be used with a variety of views, including QTableView. QSqlTableModel supports most database operations, such as reading, writing, and editing data. Here's a simple example of how to use QSqlTableModel: ```cpp // dbmodel.cpp #include <QtSql> class DbModel : public QSqlTableModel { public: DbModel(QObject *parent = nullptr, QSqlDatabase db = QSqlDatabase()) : QSqlTableModel(parent, db) { } // Override columnCount method to add custom columns int columnCount(const QModelIndex &parent = QModelIndex()) const override { return QSqlTableModel::columnCount(parent) + 1; // Add one custom column } // Override data method to display custom columns QVariant data(const QModelIndex &index, int role) const override { if (role == Qt::DisplayRole && index.column() == columnCount() - 1) return "Custom Data"; // Display custom column data return QSqlTableModel::data(index, role); } }; ``` **QTableView** QTableView is a widget that displays the data in a table format. It uses a model-view-controller (MVC) architecture to separate the data from the view. In this case, we'll use QSqlTableModel as the data model. Here's an example of how to use QTableView with QSqlTableModel: ```cpp // main.cpp #include <QtWidgets> #include <QtSql> #include "dbmodel.h" int main(int argc, char *argv[]) { QApplication a(argc, argv); // Create a QSqlDatabase object QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL"); db.setHostName("localhost"); db.setDatabaseName("test"); db.setUserName("root"); if (!db.open()) { qDebug() << "Error: " << db.lastError(); return 1; } // Create a QSqlTableModel object DbModel model; model.setTable("users"); // Set the database table model.select(); // Populate the model with data // Create a QTableView object QTableView view; view.setModel(&model); // Set the model to the view // Display the view view.show(); return a.exec(); } ``` **Example Use Case** Let's assume we want to create a database-driven application to manage user accounts. We'll use QSqlTableModel to display the user data in a QTableView. Here's the complete example code: ```cpp // main.cpp #include <QtWidgets> #include <QtSql> #include "dbmodel.h" int main(int argc, char *argv[]) { QApplication a(argc, argv); // Create a QSqlDatabase object QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL"); db.setHostName("localhost"); db.setDatabaseName("test"); db.setUserName("root"); if (!db.open()) { qDebug() << "Error: " << db.lastError(); return 1; } // Create a QSqlTableModel object DbModel model; model.setTable("users"); // Set the database table model.select(); // Populate the model with data // Create a QTableView object QTableView view; view.setModel(&model); // Set the model to the view view.horizontalHeader()->setSectionResizeMode(QHeaderView::Stretch); // Set the header section size // Display the view view.show(); return a.exec(); } ``` **Practical Takeaways** 1. QSqlTableModel is a high-level interface for accessing database data in Qt. 2. QTableView is a widget that displays data in a table format. 3. You can use QSqlTableModel with QTableView to display database data. **External Resources** * [Qt Documentation: QSqlTableModel](https://doc.qt.io/Qt-6/qsqltablemodel.html) * [Qt Documentation: QTableView](https://doc.qt.io/Qt-6/qtableview.html) **Leave a Comment or Ask for Help** If you have any questions or feedback, please leave a comment below. I'll be happy to help you. In the next topic, we'll learn about multithreading in Qt using QThread.