[SOLVED] [QColumnView] Populate widget using for loops and placeholders in PostgreSQL queries

valandil211

Hello again!

I have been trying to populate a QColumnView by using for loops and queries to my Postgres DB in conjunction. However, it seems that this code returns nothing.

@void MainWindow::ENTModels()
{
// Initially hides the groupBox
ui->ENT_groupBox->hide();

// This piece of code populates the QColumnView with a nested
// for loop. It does not work for some reason.
entmodel = new QStandardItemModel;

ENTfetch = new QSqlQuery(QSqlDatabase::database("*****"));
ENTfetch->prepare("SELECT \"ENT_Nom\" FROM \"TB_Entretien\"");
ENTfetch->exec&#40;&#41;;

TESfetch = new QSqlQuery(QSqlDatabase::database("*****"&#41;);
TESfetch->prepare("SELECT \"test\" FROM \"v_EntTest\" WHERE \"IndexEntretien\" = entretien"
                  "VALUES (?)");

// Not the best solution, as it depends upon the fact that the value of
// the PKEY is the same as the entretien number

for (int entnumber = 0; entnumber < ENTfetch->size(); ++entnumber)
{
    // Create Entretiens as first column
    ENTfetch->next();
    ent2test = new QStandardItem(ENTfetch->value(0).toString());

    TESfetch->bindValue(0, entnumber+1);
    TESfetch->exec&#40;&#41;;

    for (int tesnumber = 0; tesnumber < TESfetch->size(&#41;; ++tesnumber)
    {
        TESfetch->next();
        test2desc = new QStandardItem(TESfetch->value(0).toString());
        ent2test->appendRow(test2desc);
    }


    entmodel->appendRow(ent2test);
}
ui->ENT_entretiensColumnView->setModel(entmodel);

}@

The code seems to work when I do not use placeholders, but then it is pointless. Am I doing placeholders wrong? Can I bind values multiple times?

Thanks for your answers!

valandil211

Is there a way to pass a C++ variable in the SQL statement? I just created a PostgreSQL function that fetches the data I need and takes an integer argument.

In the code above, I want the argument of my function to be entnumber+1. Here's a code snippet (doesn't work):

@ for (int entnumber = 0; entnumber < ENTfetch->size(); ++entnumber)
{
// Create Entretiens as first column

    ENTfetch->next();
    ent2test = new QStandardItem(ENTfetch->value(0).toString());

    TESfetch->prepare("SELECT f_ent2test(entnumber+1)");
    TESfetch->exec&#40;&#41;;

    for (int tesnumber = 0; tesnumber < TESfetch->size(); ++tesnumber)
    {
        TESfetch->next();
        test2desc = new QStandardItem(TESfetch->value(0).toString());
        ent2test->appendRow(test2desc);
    }


    entmodel->appendRow(ent2test);
}

@

Now, this doesn't work. Is there a way to pass entnumber+1 to the SQL query?

Thanks!

HuXiKa

Use something like this:

@QSqlQuery qry;
qry.prepare( "SELECT f_ent2test(:id)" );
qry.bindValue( ":id", entnumber + 1 );@

valandil211

Thank you, @HuXiKa!

I guess the VALUES clause is necessary only when dealing with multiple values?