SQLITE update query fails

I am trying to update the table column by appending with new data of QtSQl database. I need to update the column imgpath by appending with new data.

Below is the code, but it always fails, what could be the issue?.

QSqlQuery query(db);
query.exec("create table table1 (id integer primary key autoincrement, time varchar(20), imgpath varchar(20))");

query.exec("insert into table1 values(NULL,'00:15:25','img0.jpg')");
query.exec("insert into table1 values(NULL,'00:15:25','img1.jpg')");

bool up = query.exec("update table1 set imgpath=concat(';newImage.jpg',imgpath) where ID=1");
if(up==false)
   qDebug()<<"Update failed";

Update:

Complete code:

     QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
     db.setDatabaseName("./newDB");
     db.open();

     QSqlQuery query(db);
     query.exec("create table table1 (id integer primary key autoincrement, time varchar(20), imgpath varchar(20))");

     query.exec("insert into table1 values(NULL,'00:15:25','img0.jpg')");
     query.exec("insert into table1 values(NULL,'00:15:25','img1.jpg')");




     //bool up = query.exec("update table1 set imgpath='newimage.jpg',time='' where ID=1");
     bool up = query.exec("update table1 set imgpath=concat(';newImage.jpg',imgpath)");
     if(up==false){
         qDebug()<<"Update failed";
         qDebug() << db.lastError();
     }

    query.exec("SELECT * FROM table1 limit 100");

     QVector<QStringList> lst;
     while (query.next())
     {
         QSqlRecord record = query.record();
         QStringList tmp;
         for(int i=0; i < record.count(); i++)
         {
             tmp << record.value(i).toString();
         }
         lst.append(tmp);
     }
     foreach (const QStringList &var, lst) {
         qDebug() << var;
     }