Qt5.2 can find the mysql driver but can not load it

[stereoMatching]

os : win7
compiler : mingw4.8(come with Qt5.2)
link to : Fedora core release 5, kernel 2.6.15-1.2054_FC5 smp on an i686

db = new QSqlDatabase();
        db->addDatabase("QMYSQL");
        db->setHostName("localhost");
        db->setDatabaseName("myclinic");
        db->setUserName("root");
        db->setPassword(",trth12");  
 
        qDebug() << loader.errorString();
        qDebug() << "drivers: "<< QSqlDatabase::drivers();
 
        if (db->open())
            qDebug() << "Success!";
        else
            qDebug() << db->lastError().text();

db = new QSqlDatabase();
        db->addDatabase("QMYSQL");
        db->setHostName("localhost");
        db->setDatabaseName("myclinic");
        db->setUserName("root");
        db->setPassword(",trth12");  
     
        qDebug() << loader.errorString();
        qDebug() << "drivers: "<< QSqlDatabase::drivers();
     
        if (db->open())
            qDebug() << "Success!";
        else
            qDebug() << db->lastError().text();

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messages

QSqlDatabase: QMYSQL driver not loaded QSqlDatabase: available
drivers: QSQLITE QMYSQL QMYSQL3 QODBC QODBC3 QPSQL QPSQL 7 “The shared
library was not found.” drivers: (“QSQLITE”, “QMYSQL”, “QMYSQL3”,
“QODBC”, “QODBC3”, “QPSQL”, “QPSQL7”)

“Driver not loaded Driver not loaded”