Qt Check if there is an open database connection

[ShapeShiftme]

Good day all.

Im currently using this code in my project to open a mysql database file

..... mydatabase.cpp....

bool myDatabase::createDatabaseConn()
{
    QSettings settings("ATSTech", "ats_shopfront");
 
    settings.beginGroup("database");
 
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
 
        db.setHostName(settings.value("server").toString());
        db.setDatabaseName("dbname");
        db.setUserName(settings.value("databaseUsername").toString());
        db.setPassword(settings.value("databasePassword").toString());
 
        if (!db.open()) {
            //QMessageBox::critical(0, QObject::tr("Database Error"), db.lastError().text());
            return false;
        }
        return true;
 
    settings.endGroup();
}

bool myDatabase::createDatabaseConn()
{
    QSettings settings("ATSTech", "ats_shopfront");

    settings.beginGroup("database");

    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");

        db.setHostName(settings.value("server").toString());
        db.setDatabaseName("dbname");
        db.setUserName(settings.value("databaseUsername").toString());
        db.setPassword(settings.value("databasePassword").toString());

        if (!db.open()) {
            //QMessageBox::critical(0, QObject::tr("Database Error"), db.lastError().text());
            return false;
        }
        return true;

    settings.endGroup();
}

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No when i use this from my other pages like so

myDatabase *getinfo = new myDatabase();
    getinfo->createDatabaseConn();

myDatabase *getinfo = new myDatabase();
    getinfo->createDatabaseConn();

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i get the following warinings/errors

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

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

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Is there any way to in the code at the top to check if there is already a connection and if so use that one instead of removing and creating a new one to the database.
im sure that would make things faster aswell

regards
Donovan Hoare

[Lesiok]

First use addDatabase like this :

bool myDatabase::createDatabaseConn()
{
    QSettings settings("ATSTech", "ats_shopfront");
 
    settings.beginGroup("database");
 
    QSqlDatabase db = QSqlDatabase::database();
    if( db.isValid() )
        return true;
 
    db = QSqlDatabase::addDatabase("QMYSQL");
 
    db.setHostName(settings.value("server").toString());
    db.setDatabaseName("dbname");
    db.setUserName(settings.value("databaseUsername").toString());
    db.setPassword(settings.value("databasePassword").toString());
 
    if (!db.open()) {
        //QMessageBox::critical(0, QObject::tr("Database Error"), db.lastError().text());
        return false;
    }
    return true;
 
    settings.endGroup();
}

bool myDatabase::createDatabaseConn()
{
    QSettings settings("ATSTech", "ats_shopfront");

    settings.beginGroup("database");

    QSqlDatabase db = QSqlDatabase::database();
    if( db.isValid() )
        return true;

    db = QSqlDatabase::addDatabase("QMYSQL");

    db.setHostName(settings.value("server").toString());
    db.setDatabaseName("dbname");
    db.setUserName(settings.value("databaseUsername").toString());
    db.setPassword(settings.value("databasePassword").toString());

    if (!db.open()) {
        //QMessageBox::critical(0, QObject::tr("Database Error"), db.lastError().text());
        return false;
    }
    return true;

    settings.endGroup();
}

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[Spitfire]

First when adding a database, name the connection:

QSqlDatabase::addDatabase( "QMYSQL", "OneNameOrOther" );

QSqlDatabase::addDatabase( "QMYSQL", "OneNameOrOther" );

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Then use that name to query for the connection:

if( QSqlDatabase::contains( "OneNameOrOther" ) )
{
    QSqlDatabase db = QSqlDatabase::database( "OneNameOrOther" );
    // now do some stuff with it
}
else
{
    // connection not found, do something
}

if( QSqlDatabase::contains( "OneNameOrOther" ) )
{
    QSqlDatabase db = QSqlDatabase::database( "OneNameOrOther" );
    // now do some stuff with it
}
else
{
    // connection not found, do something
}

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[KillGabio]

Spitfire has the answer

[ShapeShiftme]

First when adding a database, name the connection:

QSqlDatabase::addDatabase( "QMYSQL", "OneNameOrOther" );

QSqlDatabase::addDatabase( "QMYSQL", "OneNameOrOther" );

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Then use that name to query for the connection:

if( QSqlDatabase::contains( "OneNameOrOther" ) )
{
    QSqlDatabase db = QSqlDatabase::database( "OneNameOrOther" );
    // now do some stuff with it
}
else
{
    // connection not found, do something
}

if( QSqlDatabase::contains( "OneNameOrOther" ) )
{
    QSqlDatabase db = QSqlDatabase::database( "OneNameOrOther" );
    // now do some stuff with it
}
else
{
    // connection not found, do something
}

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According to your device i changed my code to this

QSettings settings("ATSTech", "StockManager");
 
    settings.beginGroup("database");
 
   /* if( QSqlDatabase::contains( "StockManagerConn" ) )
    {
        QSqlDatabase db = QSqlDatabase::database( "StockManagerConn" );
        qDebug()<<"Database Open : Using Stockmanager Connection";
        return true;
    }
    else
    {*/
 
        QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL","StockManagerConn");
 
            db.setHostName(settings.value("server").toString());
            db.setDatabaseName("stockmanager");
            db.setUserName(settings.value("databaseUsername").toString());
            db.setPassword(settings.value("databasePassword").toString());
 
 
 
            if (!db.open()) {
                QMessageBox::critical(0, QObject::tr("Database Error"), db.lastError().text());
                return false;
            }
 
            qDebug()<<"Database Opened : Started Stockmanager Connection";
            return true;
    //}
 
 
    settings.endGroup();

QSettings settings("ATSTech", "StockManager");

    settings.beginGroup("database");

   /* if( QSqlDatabase::contains( "StockManagerConn" ) )
    {
        QSqlDatabase db = QSqlDatabase::database( "StockManagerConn" );
        qDebug()<<"Database Open : Using Stockmanager Connection";
        return true;
    }
    else
    {*/

        QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL","StockManagerConn");

            db.setHostName(settings.value("server").toString());
            db.setDatabaseName("stockmanager");
            db.setUserName(settings.value("databaseUsername").toString());
            db.setPassword(settings.value("databasePassword").toString());



            if (!db.open()) {
                QMessageBox::critical(0, QObject::tr("Database Error"), db.lastError().text());
                return false;
            }

            qDebug()<<"Database Opened : Started Stockmanager Connection";
            return true;
    //}


    settings.endGroup();

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but i started getting this error

Database Opened : Started Stockmanager Connection 
QSqlQuery::exec: database not open
ERROR : inserting Company Name QSqlError(-1, "Driver not loaded", "Driver not loaded")

Database Opened : Started Stockmanager Connection 
QSqlQuery::exec: database not open
ERROR : inserting Company Name QSqlError(-1, "Driver not loaded", "Driver not loaded")

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As soon as i remove the connection name it works great.
What could i possibly be doing wrong.

Regards

[Spitfire]

You're showing wrong part of your code.
Error is generated by the part that executes a query not sets up the database.

You're probably not using connection name there.
When creating the query you have to specify which connection you want to use:

QSqlQuery query( QSqlDatabase::database( "StockManagerConn" ) );

QSqlQuery query( QSqlDatabase::database( "StockManagerConn" ) );

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otherwise it will fall back on the default name and fail.

[ShapeShiftme]

You're showing wrong part of your code.
Error is generated by the part that executes a query not sets up the database.

You're probably not using connection name there.
When creating the query you have to specify which connection you want to use:

QSqlQuery query( QSqlDatabase::database( "StockManagerConn" ) );

QSqlQuery query( QSqlDatabase::database( "StockManagerConn" ) );

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otherwise it will fall back on the default name and fail.

Thank you so much you are right.
When declaring my QSqlQuery i changed it to add the connection and it worked great.
You are a star.

[Spitfire]

I'm glad I could help

Take care!