在问数据库有关问题，大神们帮个忙啥

#include <QtCore/QCoreApplication>#include <QtSql>int main(int argc, char *argv[]){    QCoreApplication a(argc, argv);    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");    db.setDatabaseName("zhpy_table.db");    qDebug() << db.isValid();    if (db.open())    {           bool ss = false;           QSqlQuery query(db);            //query.prepare("SELECT * FROM zhcn WHERE py='jiang'");           ss=query.isActive();            query.prepare(QString("SELECT * FROM zhcn WHERE"));            if(query.exec())                    qDebug()<<QObject::tr("query success!\n");            else                    qDebug()<<query.lastError().text().toUtf8();    }    return a.exec();}