Connecting Qt with PostgreSQL: Accessing a Database Using Qt SQL

/ Qt
Manya Technologies custom GIS software development team

At Manya Technologies, we build robust, real-time applications using powerful open-source tools like Qt and PostgreSQL. One of the most common tasks in Qt-based enterprise software is database access — whether it’s reading GIS data, displaying radar tracks, or managing mission logs.

In this blog, we’ll walk you through how to connect a PostgreSQL database using Qt SQL and fetch data using simple queries.

🛠️ Prerequisites

To follow this tutorial, you should have:

  • Qt 5 or Qt 6 set up (with Qt SQL module)
  • A working PostgreSQL installation
  • A table in your PostgreSQL database for testing

Make sure the QPSQL plugin is available in your Qt installation. This is the driver that allows Qt to communicate with PostgreSQL.

📦 Sample Code: Qt PostgreSQL Connection Class

Here’s a simple class DBConnector that connects to a PostgreSQL database using QSqlDatabase:

#include "DBConnector.h"
#include <QSqlQuery>
#include <QSqlError>
#include <QDebug>

DBConnector::DBConnector(QObject *parent)
    : QObject(parent), mDatabase(QSqlDatabase::addDatabase("QPSQL"))
{
    mDatabase.setHostName("localhost");
    mDatabase.setPort(5432);
    mDatabase.setDatabaseName("mydatabase");
    mDatabase.setUserName("postgres");
    mDatabase.setPassword("mypasswd");

    if (connect()) {
        qInfo("Successfully connected to DataBase: DBConnector");
    } else {
        qDebug() << "Error Connecting to DataBase:" << mDatabase.lastError().text();
    }
}

bool DBConnector::connect()
{
    return mDatabase.open();
}

🔍 Executing a SQL Query and Fetching Results

Once connected, you can run SQL queries using QSqlQuery. Here’s an example of how to select records from a table:

void DBConnector::fetchData()
{
    QSqlQuery query("SELECT id, name FROM my_table");

    while (query.next()) {
        int id = query.value(0).toInt();
        QString name = query.value(1).toString();
        qDebug() << "ID:" << id << "Name:" << name;
    }
}

🧩 Things to Watch Out For

  • Always check if the database is open before running a query.
  • Use QSqlQuery::lastError() to debug failed queries.
  • Use parameterized queries (:param) for secure and safe SQL execution.

✅ Real-World Use Case at Manya Technologies

We use this approach in products like PrithviGIS, where real-time track data, simulation states, and sensor metadata are continuously fetched from a PostgreSQL/PostGIS backend and displayed on the Qt GUI.

Our architecture ensures:

  • No polling – Real-time updates via LISTEN/NOTIFY
  • Smooth integration with QML for dynamic UI
  • Secure database access with role-based permissions

🔚 Conclusion

Qt + PostgreSQL is a powerful combination for cross-platform application development. With just a few lines of code, you can build responsive apps that interact with large and complex datasets.

Want help building your next Qt-based software or integrating PostgreSQL into your system?

👉 Contact Manya Technologies – business@manyatechnologies.com

#QtDevelopment #PostgreSQL #QSqlDatabase #DatabaseIntegration #QtSQL #Cplusplus #SoftwareDevelopment #ManyaTechnologies #RealTimeData #GIS

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