QDateTime binding problem in QSqlQuery+QMYSQL on Qt4 vs Qt5

RazZziel

The following piece of code works as expected in Qt4, but not in Qt5:

#include <QtSql>

int main(int argc, char *argv[])
{
  QCoreApplication app(argc, argv);

  QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
  db.setHostName("localhost");
  db.setDatabaseName("test");
  db.setUserName("root");
  db.setPassword("XXXXXXXXX");

  Q_ASSERT( db.open() );

  QSqlQuery query;

  Q_ASSERT( query.exec("CREATE TABLE test ( datetime datetime )") );
  Q_ASSERT( query.exec("INSERT INTO test VALUES ( NOW() )") );

  Q_ASSERT( query.exec("SELECT * FROM test WHERE datetime != '1990/1/1 0:0:0'") );
  qDebug() << query.size();                                                                                                                                                 
  query.clear();                                                                                                                                                            
                                                                                                                                                                            
  Q_ASSERT( query.prepare("SELECT * FROM test WHERE datetime != :start") );                                                                                                 
  query.bindValue("start", "1990/1/1 0:0:0");                                                                                                                               
  Q_ASSERT( query.exec() );                                                                                                                                                 
  qDebug() << query.size();                                                                                                                                                 
  query.clear();                                                                                                                                                            
                                                                                                                                                                            
  Q_ASSERT( query.prepare("SELECT * FROM test WHERE datetime != :start") );                                                                                                 
  query.bindValue("start", QDateTime(QDate(1990,1,1), QTime(0,0,0)));                                                                                                       
  Q_ASSERT( query.exec() );
  qDebug() << query.size();
  query.clear();

  Q_ASSERT( query.exec("DROP TABLE test") );

  return 0;
}

The code just

Creates a table
Inserts one row
Tries to retrieve that row comparing its content with a date/time obviously different to the one the row contains, in three ways:
- Comparing the date/time with an inline string
- Comparing the date/time with a bound string
- Comparing the date/time with a bound QDateTime

Compiling and running for Qt4:

20:43:37 ~$ g++ -I/usr/include/qt4 -I/usr/include/qt4/QtCore -I/usr/include/qt4/QtSql -lQtCore -lQtSql sql.cpp && ./a.out 
1 
1 
1

Compiling and running for Qt5:

20:44:29 ~$ g++ -I/usr/include/qt -I/usr/include/qt/QtCore -I/usr/include/qt/QtSql -lQt5Core -lQt5Sql sql.cpp && ./a.out 
1
0
0

For some reason, every time I compare a date/time with a bound parameter, the query returns no results.

Is this an error in the QMYSQL driver that somehow went past Qt's test suites? Is this PEBCAK?

For the record:

System: Archlinux
Qt4 version: 4.8.7
Qt5 version: 5.5.1
MariaDB version: 10.0.22

RazZziel

More info: these two variations work well both in Qt4 and Qt5

  Q_ASSERT( query.prepare("SELECT * FROM test WHERE datetime != :start") );
  query.bindValue(0, QDateTime(QDate(1990,1,1), QTime(0,0,0)));
  Q_ASSERT( query.exec() );
  qDebug() << query.size();
  query.clear();
  
  Q_ASSERT( query.prepare("SELECT * FROM test WHERE datetime != ?") );
  query.addBindValue(QDateTime(QDate(1990,1,1), QTime(0,0,0)));
  Q_ASSERT( query.exec() );
  qDebug() << query.size();
  query.clear();

RazZziel

Okay, found the problem: this

query3.bindValue("start", "1990/1/1 0:0:0");

needs to be changed to

query3.bindValue(":start", "1990/1/1 0:0:0");

That works in both Qt4 and Qt5. This is actually consistent with the documentacion of both Qt4 and Qt5

http://doc.qt.io/qt-4.8/qsqlquery.html#bindValue
http://doc.qt.io/qt-5/qsqlquery.html#bindValue

Note that the placeholder mark (e.g :) must be included when specifying the placeholder name.

But looks like Qt5 enforces the restriction while Qt4 doesn't.