Sqlite connection QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.
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wrote on 1 Aug 2012, 15:31 last edited by
You may want to look "here":http://qt-project.org/forums/viewthread/18722/.
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wrote on 1 Aug 2012, 15:39 last edited by
you just have to call it in the ctor of you class i think
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wrote on 1 Aug 2012, 15:39 last edited by
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.
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wrote on 29 Jun 2014, 14:34 last edited by
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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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"));@
wrote on 7 May 2023, 06:17 last edited byHi
I have the sampe problem and I solve it by this command :
if (QSqlDatabase::contains("NameOfConnection"))
{
QSqlDatabase::removeDatabase("NameOfConnection");
return
}
QSqlDatabase::addDatabase("QSQLITE", "NameOfConnection");
I hope it will beuseful. -
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;}
@Your call to removeDatabase() is wrong - it takes the database connection name, not a filename: https://doc.qt.io/qt-6/qsqldatabase.html#removeDatabase
Also why do you call add/removeDatabase every time instead openening it once as described in the documentation?
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Your call to removeDatabase() is wrong - it takes the database connection name, not a filename: https://doc.qt.io/qt-6/qsqldatabase.html#removeDatabase
Also why do you call add/removeDatabase every time instead openening it once as described in the documentation?
wrote on 7 May 2023, 09:00 last edited bythaks you for ur answer, we use it for our unit test.
I have another question abou threading may i ask u? -
thaks you for ur answer, we use it for our unit test.
I have another question abou threading may i ask u?@nasimChildOfDesert said in Sqlite connection QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.:
I have another question abou threading may i ask u?
You have to create a new db connection per thread. There are a lot of threads about this in the forum.
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@nasimChildOfDesert said in Sqlite connection QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.:
I have another question abou threading may i ask u?
You have to create a new db connection per thread. There are a lot of threads about this in the forum.
wrote on 7 May 2023, 09:19 last edited by@Christian-Ehrlicher
no imean do you know agood document about threading, mutex, socketprograming TCP
there are a lot of info on the net but most of them are not complete and no practical sample -
@Christian-Ehrlicher
no imean do you know agood document about threading, mutex, socketprograming TCP
there are a lot of info on the net but most of them are not complete and no practical sample@nasimChildOfDesert said in Sqlite connection QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.:
threading, mutex, socketprograming TCP
You don't need threading for sockets/tcp when you use Qt. Seaching for 'Qt threading' or looking at the QTcpSocket documentation should be a good start.