Connecting to Database in Qt

[jsulm]

@Swati777999 said in Connecting to Database in Qt:

what to use whether SQL Model Class or QTableview?

Both.
Please see how it is done here: https://doc.qt.io/qt-5/qsqltablemodel.html

[Swati777999]

@jsulm said in Connecting to Database in Qt:

@Swati777999 said in Connecting to Database in Qt:

what to use whether SQL Model Class or QTableview?

Both.
Please see how it is done here: https://doc.qt.io/qt-5/qsqltablemodel.html

I used this strategy but I am not getting anything in my main window. :(

[jsulm]

@Swati777999 Then you are doing something wrong and should provide more information to get meaningful answer.
Best would be related code.

[Swati777999]

@jsulm

#include "dbmanager.h"

DbManager::DbManager(const QString &path)
{ Q_UNUSED(path);
m_db = QSqlDatabase::addDatabase("QSQLITE");
m_db.setDatabaseName("C:/Users/ss/Desktop/TestData.db");

if (!m_db.open())
{
qDebug() << "Error: connection with database failed";
}
else
{
qDebug() << "Database: connection ok";
}
}
bool DbManager::addEntry(const QString &name)
{
bool success = false;
QSqlQuery query;
query.prepare("INSERT INTO TestData VALUES (:time)");
query.bindValue(":time, time);
if(query.exec())
{
success = true;
}
else
{
qDebug() << "addtemperature error:"
<< query.lastError();
}

return success;
qDebug() << query.isValid();

QSqlQueryModel model;
   model.setQuery("SELECT * FROM TestData");

 for (int i = 0; i < model.rowCount(); ++i) {
    int id = model.record(i).value("id").toInt();
   QString name = model.record(i).value("time").toString();
   qDebug() << id << time;
   }

   QLabel *labelExp = new QLabel(this);
   labelExp->setFrameStyle(QFrame::Panel | QFrame::Sunken);
   labelExp->setText("first line\nsecond line");
   labelExp->setAlignment(Qt::AlignBottom | Qt::AlignRight);

   //Named binding
   QSqlQuery query1;
   query1.prepare("INSERT INTO TestData (time,temperature) VALUES (:time, "
                  ":temperature)");
   query1.bindValue(":time","2020-11-31 10:19:38");
   query1.bindValue(":temperature", 27.4);
   query1.exec();

   //Positional Binding
   QSqlQuery query2;
   query2.prepare("INSERT INTO TestData (time,temperature) VALUES (?, ?, )");
   query2.addBindValue("2010-06-31 12:08:35");
   query2.addBindValue(30.6);
   query2.exec();

   QSqlQueryModel *model1 = new QSqlQueryModel;
      model1->setQuery("SELECT time, temperature FROM TestData");
      model1->setHeaderData(0, Qt::Horizontal, tr("Time"));
      model1->setHeaderData(1, Qt::Horizontal, tr("Temperature"));

      QTableView *view = new QTableView;
      view->setModel(model1);
      view->show();

      model1->setHeaderData(0, Qt::Horizontal, QObject::tr("Time"));
      model1->setHeaderData(1, Qt::Horizontal, QObject::tr("Temperature"));

}

[jsulm]

@Swati777999 said in Connecting to Database in Qt:

QSqlQueryModel model;

Your model is a local variable and is destroyed as soon as it goes out of scope.
And please format you code properly.

[Pl45m4]

@jsulm

For whatever reason there are two models... QSqlQueryModel model and QSqlQueryModel* model1

[Swati777999]

@jsulm I didn't get your point clearly and how to format the code; do you mean looking after the indentation/ improving the readability of the codes?

[Swati777999]

@Pl45m4 I was trying to see how QSqlQuery and QSqlQueryModel are different from each other, no other reason apart from that.

[JonB]

@Swati777999 said in Connecting to Database in Qt:

I didn't get your point clearly and how to format the code; do you mean looking after the indentation/ improving the readability of the codes?

When pasting code please select it all and use the the </> Code button:

so it comes out like this
with ``` above & below it in your post

As for your code. addEntry() at least does little --- most of the code is not executed --- since you have an unconditional return statement before most of the body. If people are supposed to look at this for you, you should really clear it up a lot before posting.

[jsulm]

@Swati777999 said in Connecting to Database in Qt:

I didn't get your point clearly

We are talking about absolute C++ basics now! Please learn those!

bool DbManager::addEntry(const QString &name)
{
...
QSqlQueryModel model;
...
}

In the code above "model" only exists inside DbManager::addEntry. As soon as DbManager::addEntry is done "mode" goes out of scope and is deleted!
Also, I see that you do "return success;" before you create your model - how can this work at all?!