Important: Please read the Qt Code of Conduct - https://forum.qt.io/topic/113070/qt-code-of-conduct
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"); database->setDatabaseName(dataBaseFile); qDebug() << dataBaseFile; if(!database->open()) { QMessageBox::warning(0,"Error","Couldn't open setting database"); //qApp->setProperty("DatabaseOpen","ERROR"); } // read data QSqlQuery result (Query, *database); //close database; QString connname = database->connectionName(); database->close(); database->removeDatabase(dataBaseFile); 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":http://qt-project.org/forums/viewthread/18722/.
-
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":http://doc.qt.nokia.com/4.7-snapshot/qsqldatabase.html#details.
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"));@