Hi all,

i can't understand where's my mistake.

Qt Code: 
  1. #include <QApplication>
  2. #include <QtSql>
  3. #include <QtWidgets/QMessageBox>
  4.  
  5. bool m_hastransaction     = false;
  6. bool m_startedtransaction = false;
  8.  
  9.  
  10. void connection()
  11. {
  12.     db = QSqlDatabase::addDatabase("QSQLITE");
  13.     db.setDatabaseName(":memory:");
  14.     m_startedtransaction = false;
  15.     m_hastransaction     = false;
  16.     if (!db.open()) {
  17.         QMessageBox::critical(0, qApp->tr("Cannot open database"),
  18.             qApp->tr("Unable to establish a database connection.\n"
  19.                      "This example needs SQLite support. Please read "
  20.                      "the Qt SQL driver documentation for information how "
  21.                      "to build it.\n\n"
  22.                      "Click Cancel to exit."), QMessageBox::Ok);
  23.         return;
  24.     }
  25.     m_hastransaction = db.driver()->hasFeature(QSqlDriver::Transactions);
  26. }
  27.  
  28. void startTransaction()
  29. {
  30.     if(m_hastransaction)
  31.         m_startedtransaction =  db.transaction();
  32. }
  33.  
  34. bool endTransaction(bool value)
  35. {
  36.     if(!m_hastransaction || !m_startedtransaction)
  37.         return value;
  38.     else{
  39.         if(value)
  40.         {
  41.             db.commit();
  42.         }else{
  43.             db.rollback();
  44.         }
  45.         m_startedtransaction = false;
  46.     }
  47.     return value;
  48. }
  49.  
  50. bool UnloggedQueryExec(QString query,bool setForward)
  51. {//it doesn't work
  52.     startTransaction();
  53.     QSqlQuery q(query);//QSqlQuery q = QSqlQuery(query);//it's the same
  54.     q.setForwardOnly(setForward);
  55.     bool ret = q.exec();
  56.     if(!ret){
  57.         qDebug() << "*** UnloggedQueryExec: query failed: " << query << q.lastError().text();
  58.     }else{
  59.         qDebug() << "*** UnloggedQueryExec: query ok";	
  60. 	}
  61.     return endTransaction(ret);
  62. }
  63.  
  64. bool UnloggedQueryExec1(QString query,bool setForward)
  65. {//it works
  66.     startTransaction();
  68.     q.setForwardOnly(setForward);
  69.     bool ret = q.exec(query);
  70.     if(!ret){
  71.         qDebug() << "*** UnloggedQueryExec1: query failed: " << query << q.lastError().text();
  72.     }else{
  73.         qDebug() << "*** UnloggedQueryExec1: query ok";	
  74. 	}
  75.     return endTransaction(ret);
  76. }
  77.  
  78. int main(int argc, char *argv[])
  79. {
  80.     QApplication a(argc,argv);
  81.  
  82.     connection();
  83.     UnloggedQueryExec("CREATE TABLE log(id INTEGER PRIMARY KEY,descr varchar(30))",true);
  84.     UnloggedQueryExec1("CREATE TABLE log(id INTEGER PRIMARY KEY,descr varchar(30))",true);
  85.  
  86.     return a.exec();
  87. }
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Qt Code: 
  1. Output:
  2. *** UnloggedQueryExec: query failed:  "CREATE TABLE log(id INTEGER PRIMARY KEY,descr varchar(30))" "table tipolog already exists Unable to fetch row"
  3. *** UnloggedQueryExec1: query ok
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EDIT: ops i forget pro file, even if it should not matter:

Qt Code: 
  1. QT         += core widgets sql
  2. CONFIG     += console
  3. TARGET      = test
  4. TEMPLATE    = app
  5.  
  6. SOURCES    += main.cpp 
  7.  
  8. OBJECTS_DIR = build/o
  9. MOC_DIR     = build/moc
  10. UI_DIR      = build/ui
  11. RCC_DIR     = build/rcc
  12. DESTDIR     = bin
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Someone could be so kind to help me?
Thanks in advance,
Alberto