I'm using QtSql (sqlite database in memory) and I need to remove the first column from my tables. Unfortunately, when I do this and I attempt to change a value using setData() I get a "QSqlQuery::value: not positioned on a valid record" error yet I'm able to retreive the current valus using a call to data() using the exact same QModelIndex. Has anyobody ever seen this problem or have a work around? Below is an example which show the problem. To remove the first column, you just need to run the compiled binary with at least one argument:

Qt Code: 
  1. #include <QtGui>
  2. #include <QtSql>
  3. #include <QWidget>
  4. #include <QDebug>
  5. #include <iostream>
  6.  
  7.  
  8.  
  9.  
  10.  int main(int argc, char *args[])
  11.  {
  12.     QApplication app(argc, args);
  13.  
  14.     // Create an im memory database
  15.     QSqlDatabase db = QSqlDatabase::addDatabase( "QSQLITE" );
  16.     db.setDatabaseName( ":memory:" );
  17.     if ( !db.open() )
  18.     {
  19.         qCritical( "ERROR in opening the internal database" );
  20.     }
  21.  
  22.     // Create a table in the database
  23.     QSqlQuery query = db.exec(QString("create table test (id INTEGER PRIMARY KEY AUTOINCREMENT)"));
  24.     // Add a column in the table using a query
  25.     query.exec("ALTER TABLE test ADD col2 VARCHAR(50);");
  26.     query.exec("ALTER TABLE test ADD col3 VARCHAR(50);");
  27.     // Add a row to the column
  28.     query.exec("INSERT INTO test ('col2','col3') VALUES ('something','last');");
  29.  
  30.  
  31.  
  32.     bool removeFirstColumn = argc > 1;
  33.  
  34.     // Create a table model for the table view
  36.     model->setTable("test");
  37.     model->setEditStrategy(QSqlTableModel::OnFieldChange);
  38.     if (removeFirstColumn) {
  39.         model->removeColumns(0,1);
  40.     }
  41.     model->select();
  42.     // Cteate a table view and display it
  43.     QTableView table;
  44.     table.setModel(model);
  45.     table.show();
  46.  
  47.  
  48.  
  49.     int row = 0;
  50.     int col ;
  51.     if (removeFirstColumn) {
  52.         col = 1 ;
  53.     } else {
  54.         col = 2;
  55.     }
  56.     QModelIndex index = model->index(row, col);
  57.     //NOTE: current value should be "last", this works
  58.     qDebug() << "value before change at row=" << row << "col=" << col << model->data( index ).toString();
  59.  
  60.  
  61.     //Attempt to change the value
  62.     QVariant newValue = "new value";
  63.     model->setData( index, newValue);
  64.     qDebug() << "value after change at row=" << row << "col=" << col << model->data( index ).toString();
  65.  
  66.     return app.exec();
  67.  }
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Below is my output:
C:\Qt\examples\sql>sql remove
value before change at row= 0 col= 1 "last"
QSqlQuery::value: not positioned on a valid record
value after change at row= 0 col= 1 "last"