@mrjj Ok so, it seems that it doesn't detect the table "usuarios" even though it's there...
So in my sqlite editor I executed the command and it worked properly:
http://s18.postimg.org/iqry91pmx/image.png
EDIT: I solved that problem: the program was searching the db in the remote directory not in the real directory, now it doesn't says any error but It doesn't shows the information.
I've tried (SELECT * FROM usuarios) but nothing, it doesn't works.
2ND EDIT: I solved the problem, it was on my printing method, I tried a much simpler methor by doing:
int i=0;
while (query.next()) {
ui->tableWidget->setItem(i,0,new QTableWidgetItem(query.value(0).toString()));
ui->tableWidget->setItem(i,1,new QTableWidgetItem(query.value(1).toString()));
ui->tableWidget->setItem(i,2,new QTableWidgetItem(query.value(2).toString()));
i++;
ui->tableWidget->insertRow(i);
}
Thank you for your help.