QSqlQuery::isValid returns false

[wysota]

No, I mean Access databases can't jump across the result set regardless if you use Qt or not. If you want to reach the last entry, you have to iterate each record one by one until you reach the end.

[mismael85]

but i have the program that deal with access database which is built using visual basic
and this program go through the database easy it make last , first, next and previous
and i want to rebuild this program using c++. it means that the database support non sequential access
as well as sequential.

[wysota]

Maybe it emulates last() using next(). It doesn't say anything about either the database or the ODBC driver that handles it.

[haldrik]

Hello, I have a similar problem with an sqlite3 database.

Queries work fine interactively, even queries work fine on the constructor, but on a slot give me this messages on console output:

QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record
QSqlQuery::value: not positioned on a valid record

I think each message is one for each field in the query string.

The query is executed and the values are retrived, I can use this values without problems, but this messages bothers me, and dirty my console output.

here the implementation of the slot:

void ThirdParties::setLoans(QString id)
{
	qDebug() << id;	
	QSqlQuery queryLoans;
	queryLoans.prepare("SELECT loan_id, date, value, quotas, cancel_quotas, loan_type FROM tblLOANS WHERE thirdparty_id=:id");
	queryLoans.bindValue(":id", id);
	if (!queryLoans.exec())
		QMessageBox::warning(this, tr("Error en la consulta"), queryLoans.lastError().text());
	loanIdComboBox->clear();
	dateEdit->clear();
	valueLineEdit->clear();
	quotasLineEdit->clear();
	cancelQuotasSpinBox->clear();
 
	while (queryLoans.next())
	{
		qDebug() << queryLoans.value(0).toString();
		loanIdComboBox->addItem(queryLoans.value(0).toString());
	}
	queryLoans.first();	
	dateEdit->setDate(queryLoans.value(1).toDate());
	valueLineEdit->setText(queryLoans.value(2).toString());	
	quotasLineEdit->setText(queryLoans.value(3).toString());
     loanTypeComboBox->setCurrentIndex(loanTypeComboBox->findText(queryLoans.value(5).toString()));
	cancelQuotasSpinBox->setValue(queryLoans.value(4).toInt());
}

void ThirdParties::setLoans(QString id)
{
	qDebug() << id;	
	QSqlQuery queryLoans;
	queryLoans.prepare("SELECT loan_id, date, value, quotas, cancel_quotas, loan_type FROM tblLOANS WHERE thirdparty_id=:id");
	queryLoans.bindValue(":id", id);
	if (!queryLoans.exec())
		QMessageBox::warning(this, tr("Error en la consulta"), queryLoans.lastError().text());
	loanIdComboBox->clear();
	dateEdit->clear();
	valueLineEdit->clear();
	quotasLineEdit->clear();
	cancelQuotasSpinBox->clear();

	while (queryLoans.next())
	{
		qDebug() << queryLoans.value(0).toString();
		loanIdComboBox->addItem(queryLoans.value(0).toString());
	}
	queryLoans.first();	
	dateEdit->setDate(queryLoans.value(1).toDate());
	valueLineEdit->setText(queryLoans.value(2).toString());	
	quotasLineEdit->setText(queryLoans.value(3).toString());
     loanTypeComboBox->setCurrentIndex(loanTypeComboBox->findText(queryLoans.value(5).toString()));
	cancelQuotasSpinBox->setValue(queryLoans.value(4).toInt());
}

To copy to clipboard, switch view to plain text mode 

[jacek]

Do the errors disappear when you comment out lines #20--#25?

[haldrik]

Don't dessapear. Even I commented all lines exept the declaration, prepare-bindValue and executed lines of the query, the message still appear.

I repeat, this message appear only in this slot, on the constructor don't appear.

[haldrik]

Hello. Now I solved my problem.

The problem is using multiple connections (QObject::connect), the slot avobe call other signal i.e:

connect(idComboBox, SIGNAL(currentIndexChanged(QString)),
			this, SLOT(setLoans(QString)));	
 
	connect(loanIdComboBox, SIGNAL(currentIndexChanged(int)),
			this, SLOT(setLoanValues(int)));

connect(idComboBox, SIGNAL(currentIndexChanged(QString)),
			this, SLOT(setLoans(QString)));	

	connect(loanIdComboBox, SIGNAL(currentIndexChanged(int)),
			this, SLOT(setLoanValues(int)));

To copy to clipboard, switch view to plain text mode 

loanIdComboBox->clear(); call currentIndexChanged, on that connection I have the same query and for this behavior was the error.

I correct this behavior using at begin of slot loanIdComboBox->blockSignals(true) and then on final of slot loanIdComboBox->blockSignals(false).

DBG is a great help.