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Sqlite connection QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.

  • Hello Gurus,

    I am trying to fetch data from an SQLite database, it works fine, however when I try to call the function again it works but with an debug message

    QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.

    here is my code, do I close the connection correctly? thanks

    @QSqlQuery MainForm::QuerydB(QString Query, QString dataBaseFile)
    //QSqlQuery result;
    //QString dbname;

    database = new QSqlDatabase();
    //set database driver to QSQLITE
    *database = QSqlDatabase::addDatabase("QSQLITE");
    qDebug() << dataBaseFile;
        QMessageBox::warning(0,"Error","Couldn't open setting database");
     // read data
     QSqlQuery result (Query, *database);
    //close database;
     QString connname = database->connectionName();
     delete database;
     return result;


  • I think you have to call QSqlDatabase::addDatabase("QSQLITE"); once in your program

  • But how can I then make it inform of a function?

  • You may want to look "here":

  • you just have to call it in the ctor of you class i think

  • Normally you don't need to open the database connection more than once within your application. You also want to look at the sample code "here":

    Since each database connection will only have a single instance within the whole application you are able to access it via QSqlDatabase::connection().

    I would suggest that you have three static functions in your MainForm. One that opens the database connection, one the exectues a query and the third to close the database. The first and the third are called i.e. in the MainForm constructor/destructor, as Neutron Stern wrote, the second whenever you need a query.

    Please read the mentioned documentation there you will find the needed help.

  • For all people who looks for a good solution, this is what i found, tried and works fine:
    (PS : I have an application, which has more then one project in it, means more then one sql-connection)

    Call addDatabase() only once in your application (see second parameter, can be anything)

    @QSqlDatabase::addDatabase("QSQLITE", "MyDBConnectionName");@

    Do this first whenever you want to do some stuff with your DB

    @if (QSqlDatabase::contains("MyDBConnectionName"))
    ...e.g. query@

    Now you must get an instance to db-object

    @QSqlDatabase sqlDatabase = QSqlDatabase::database("MyDBConnectionName");@

    Add DB information to your query

    @QSqlQuery query(QSqlDatabase::database("MyDBConnectionName"));@

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