qsqlquery UPDATE how to?

[unix7777]

I read all the documentation of QSqlQuery and all topics in the net.Unfortunately there are examples only with INSERT or SELECT statement.
I have the code below working:

QSqlQuery query;
    query.prepare("INSERT INTO clients (ClientName, ClientCity, ClientAddress, ClientMol, ClientEik, ClientVat, ClientTel, ClientMail)"
            "VALUES (?, ?, ?, ?, ?, ?, ?, ?)");
    query.addBindValue(ui->lineEdit_name->text());
    query.addBindValue(ui->lineEdit_city->text());
    query.addBindValue(ui->lineEdit_address->text());
    query.addBindValue(ui->lineEdit_mol->text());
    query.addBindValue(ui->lineEdit_eik->text());
    query.addBindValue(ui->lineEdit_vat->text());
    query.addBindValue(ui->lineEdit_tel->text());
    query.addBindValue(ui->lineEdit_mail->text());
    query.exec();

QSqlQuery query;
    query.prepare("INSERT INTO clients (ClientName, ClientCity, ClientAddress, ClientMol, ClientEik, ClientVat, ClientTel, ClientMail)"
            "VALUES (?, ?, ?, ?, ?, ?, ?, ?)");
    query.addBindValue(ui->lineEdit_name->text());
    query.addBindValue(ui->lineEdit_city->text());
    query.addBindValue(ui->lineEdit_address->text());
    query.addBindValue(ui->lineEdit_mol->text());
    query.addBindValue(ui->lineEdit_eik->text());
    query.addBindValue(ui->lineEdit_vat->text());
    query.addBindValue(ui->lineEdit_tel->text());
    query.addBindValue(ui->lineEdit_mail->text());
    query.exec();

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What i need is the same but with UPDATE and as condition WHERE ROWID=rowid
I don't know where to put this WHERE and where the value of rowid.I have tried a lot.