[Solved} WHERE clause Qstring

[andrewhopps]

Table layout example:

@[product][quantity1][ piece1][quantity2][ piece2]
[003893][ 1 ][003852][ 2 ][003845 ]@

Query attempt:

@ query->prepare("SELECT quantity1 FROM prints WHERE product = ?");
query->bindValue(0, selectedPrint);@

Query Result:

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

I am trying to return the number from the quantity1 column, using a variable.

My variable is the text string of my currently selected list view item:
@QString selectedPrint = ui->listView->model()->data(index).toString();@

How do I use a string variable in my query?

[Saugglocke]

Hey,

does it work without the prepare?

If not, then please show how you retrieve the records.

bb

[JKSH]

Hi,

Did you run QSqlQuery::exec() and QSqlQuery::next() before QSqlQuery::value() ?

See "the documentation":http://qt-project.org/doc/qt-5/qsqlquery.html for examples.

[andrewhopps]

Retrieval to populate product list:
@ QSqlQueryModel* modal=new QSqlQueryModel();
QSqlQuery* query=new QSqlQuery(db);

    query->prepare("SELECT product FROM prints");

    query->exec();
    modal->setQuery(*query);
    ui->listView->setModel(modal);@

Entire ListView that is main part of form:
@void printdb::on_listView_clicked(const QModelIndex &index)
{
QString selectedPrint = ui->listView->model()->data(index).toString();
QString direct = "prints/" % selectedPrint % ".jpg";
QPixmap g(direct);

scene = new QGraphicsScene(this);
ui->graphicsView->setScene(scene);
ui->graphicsView->setDragMode(QGraphicsView::ScrollHandDrag);
scene->addPixmap(g);

QString number = QString("%1").arg(selectedPrint.toInt(), 2, 10, QChar('0'));
QSqlQuery* query=new QSqlQuery(db);
query->prepare("SELECT quantity1 FROM prints WHERE product = ?");
query->bindValue(0, selectedPrint);
if(query->exec())
{
    ui->lineEdit_2->setText(query->value(0).toString());
}
else
    qDebug() << query->lastError();@

Running without prepare statement I get
@QSqlError("", "Parameter count mismatch", "")@

[JKSH]

You need to call QSqlQuery::next() before QSqlQuery::value().

---

By the way, you don't have to create QSqlQuery on the heap.
@
// Replace this...
QSqlQuery* query=new QSqlQuery(db);

// ...with this...
QSqlQuery query(db);
@