QSqlQuery and QLineEdit

[GuL]

Why this code doesn't work?
I want to show the result of this query in the QLineEdit.

void testeMYSQL2::on_pushButton_clicked()
{
	QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
        db.setHostName("localhost");
        db.setDatabaseName("teste");
        db.setUserName("root");
        db.setPassword("");
	db.open();
/*	if (!db.open()){
		QMessageBox::critical(0, tr("Error"), 
		QString("The error:\n%1").arg(db.lastError().text())); 
	 }
	 else{
		QMessageBox::information(0, tr("OK"), QString("The is NO error\n"));
	 }
*/
	 QSqlQuery query;
	 query.exec("select nome_prod from produtos where cod_prod = 1");
	query.next();
	for (int i = 0; i < record.count(); i++) {
		QString name = query.value(i).toString();
		nameEdit->setText(name);
	}

void testeMYSQL2::on_pushButton_clicked()
{
	QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
        db.setHostName("localhost");
        db.setDatabaseName("teste");
        db.setUserName("root");
        db.setPassword("");
	db.open();
/*	if (!db.open()){
		QMessageBox::critical(0, tr("Error"), 
		QString("The error:\n%1").arg(db.lastError().text())); 
	 }
	 else{
		QMessageBox::information(0, tr("OK"), QString("The is NO error\n"));
	 }
*/
	 QSqlQuery query;
	 query.exec("select nome_prod from produtos where cod_prod = 1");
	query.next();
	for (int i = 0; i < record.count(); i++) {
		QString name = query.value(i).toString();
		nameEdit->setText(name);
	}

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What I am doing wrong?

Renan

[spirit]

at first, you have only one column (according to your query text)
second, you set position only on first record (query.next())
and then try to read data from non-existed columns (you have only one column!)
so, try this code

....
     while (query.next()) {
         QString data = query.value(0).toString();//first column == nome_prod
         ....
     }
     ....

....
     while (query.next()) {
         QString data = query.value(0).toString();//first column == nome_prod
         ....
     }
     ....

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read for detailes QSqlQuery::next

[GuL]

The result of this query is only one line and one column...

The result is DISCO1

I just want to see this word in the QLineEdit, thats why I didn't use the while loop.
Why the result doesn't show? What signal/slot should I use?
Signal->clicked()
Slot-> ???

Renan

[spirit]

if you need only one result, then

query.next();
QString res = query.valut(0).toString();

query.next();
QString res = query.valut(0).toString();

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[wysota]

I don't know what "record" is in your case, but I'd guess it's an invalid QSqlRecord with a count of 0, thus your loop never gets executed. I'd suggest doing it the way spirit said.

[GuL]

New code and still no result:

void testeMYSQL2::on_pushButton_clicked()
{
	QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
        db.setHostName("localhost");
        db.setDatabaseName("teste");
        db.setUserName("root");
        db.setPassword("teste1234");
	db.open();
/*	if (!db.open()){
		QMessageBox::critical(0, tr("Error"), 
		QString("The error:\n%1").arg(db.lastError().text())); 
	 }
	 else{
		QMessageBox::information(0, tr("OK"), QString("The is NO error\n"));
	 }
*/
	 QSqlQuery query;
	 query.exec("select nome_prod from produtos where cod_prod = 1");
 
	query.next();
		QString name = query.value(0).toString();
		nameEdit->setText(name);
}

void testeMYSQL2::on_pushButton_clicked()
{
	QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
        db.setHostName("localhost");
        db.setDatabaseName("teste");
        db.setUserName("root");
        db.setPassword("teste1234");
	db.open();
/*	if (!db.open()){
		QMessageBox::critical(0, tr("Error"), 
		QString("The error:\n%1").arg(db.lastError().text())); 
	 }
	 else{
		QMessageBox::information(0, tr("OK"), QString("The is NO error\n"));
	 }
*/
	 QSqlQuery query;
	 query.exec("select nome_prod from produtos where cod_prod = 1");
	
	query.next();
		QString name = query.value(0).toString();
		nameEdit->setText(name);
}

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[spirit]

void testeMYSQL2::on_pushButton_clicked()
{
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
        db.setHostName("localhost");
        db.setDatabaseName("teste");
        db.setUserName("root");
        db.setPassword("teste1234");
    if (!db.open()) {
          qDebug() << query.lastError().text();
          return;
    }
 
     QSqlQuery query;
     if (!query.exec("select nome_prod from produtos where cod_prod = 1")) {
          qDebug() << query.lastError().text();
          return;
     }
 
        if (!query.next()) {
          qDebug() << query.lastError().text();
          return;
        }
        QString name = query.value(0).toString();
        nameEdit->setText(name);
}

void testeMYSQL2::on_pushButton_clicked()
{
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
        db.setHostName("localhost");
        db.setDatabaseName("teste");
        db.setUserName("root");
        db.setPassword("teste1234");
    if (!db.open()) {
          qDebug() << query.lastError().text();
          return;
    }

     QSqlQuery query;
     if (!query.exec("select nome_prod from produtos where cod_prod = 1")) {
          qDebug() << query.lastError().text();
          return;
     }
    
        if (!query.next()) {
          qDebug() << query.lastError().text();
          return;
        }
        QString name = query.value(0).toString();
        nameEdit->setText(name);
}

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run this code and show console messages.

[GuL]

gul@gul-laptop:~/qt/testemysql2$ ./testemysql2
QSqlQuery::exec: database not open
"Driver not loaded Driver not loaded"

=-=-=-=-=-=-==-=-=-=-

It doesn't show any messages:

gul@gul-laptop:~/qt/testemysql2$ ./testemysql2

[spirit]

did you have compiled plugin or qt with mysql driver?

[GuL]

It is working.

#
void testeMYSQL2::on_pushButton_clicked()
{
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
        db.setHostName("localhost");
        db.setDatabaseName("teste");
        db.setUserName("root");
        db.setPassword("teste1234");
    if (!db.open()) {
          qDebug() << query.lastError().text();
          return;
    }
 
     QSqlQuery query;
     if (!query.exec("select nome_prod from produtos where cod_prod = 1")) {
          qDebug() << query.lastError().text();
          return;
....
     }

#
void testeMYSQL2::on_pushButton_clicked()
{
    QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
        db.setHostName("localhost");
        db.setDatabaseName("teste");
        db.setUserName("root");
        db.setPassword("teste1234");
    if (!db.open()) {
          qDebug() << query.lastError().text();
          return;
    }

     QSqlQuery query;
     if (!query.exec("select nome_prod from produtos where cod_prod = 1")) {
          qDebug() << query.lastError().text();
          return;
....
     }

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this line, the fisrt one: qDebug() << query.lastError().text();

should be: qDebug() << db.lastError().text();

to compile.
because it is testing its connection

never mind., but it doesn't show anything to me.

[GuL]

what can I do to get those lastError() ???

Renan

[spirit]

does qDebug() << db.lastError().text(); return nothing?
if QSqlDatabase::lastError doesn't return anything then everything is ok.