I've installed QT 5.4.1 and working in QT Creator 3.3.2.

I'm getting this error code:
C:\www\QtGui\testMysqlConnection\main.cpp:28: error: undefined reference to `_imp___ZN12QSqlDatabaseC1Ev'

line 28 has these lines of code (qDebug() << "Connected!";
QSqlQuery query;
query.exec("SELECT fname FROM client");
)
The includes:
#include <QCoreApplication>
#include <QtSql/QSql>
#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlDriver>
#include <QtSql/QSqlQuery>
#include <QDebug>

Thanks for your help.