HI ,
I am using QT4.4 with visual studio 2005. My problem is that how the query is going to executes on database. I am having two files ,main.cpp and connection.h

In connection.h I created a connection and opened it.

connection.h
Qt Code: 
  1. bool creatconnection()
  2. {
  3.  QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
  4.      db.setHostName("bigblue");
  5.      db.setDatabaseName("flightdb");
  6.      db.setUserName("acarlson");
  7.      db.setPassword("1uTbSbAs");
  8.      bool ok = db.open();
  9.      QSqlQuery.exec(" create table sample(id Integer , Name varchar) ");
  10.      retutn true;
  11. }
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Now in main.cpp I called this function to open and executed one query
main.cpp
Qt Code: 
  1. #include <QtGui>
  2.  
  3.  #include "../connection.h"
  4.  
  5.  int main(int argc, char *argv[])
  6.  {
  7.      QApplication app(argc, argv);
  8.  
  9.      if (!createConnection())
  10.          return 1;
  11.  
  12.     QSqlQuery.exec(" select * from sample ");
  13.  
  14.      return app.exec();
  15.  }
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Every thing is working fine .My doubt is how the query in main.cpp firing on database which I have created in connection.h with out providing the QSqldatabase object. I read the documentation regrading QTSQL module ,which it provides that it call default database. But Here I am not executing query in connection.h ,I am executing in main.cpp ,here how it is able to fire on a particular database in main.cpp.
So I am very much confused about How it is working . Please help me to come out off this confusion.

Please suggest me to solve this problem

Regards,
Sudheer.