What is the error and how to fix it when connecting and getting data from the database through QT?

Question

SQL

I connect the database to the program, when I try to click on the button to get data from the database, some error pops up:
QSqlDatabasePrivate::addDatabase: duplicate connection name 'qt_sql_default_connection', old connection removed.
please tell me why it occurs and how to fix it?
main.cpp code

#include "mainwindow.h"
#include "ui_mainwindow.h"
#include "QtSql/QSqlDatabase"
#include "QSqlQuery"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);

 //   QSqlDatabase database = QSqlDatabase::addDatabase("QSQLITE");
   // database.setDatabaseName("C:Users/NikaB/Desktop/blabla/TestSQL/database.db3");
   // if (!database.open())
     //   ui->label->setText("open the database");
   // else
     //   ui->label->setText("connected...");
}
void MainWindow::on_pushButton_clicked()
{
    QSqlDatabase db;
    db = QSqlDatabase::addDatabase("QSQLITE");
    db.setDatabaseName("baza/database.db3");
    db.open();

    //Осуществляем запрос
    QSqlQuery query;
    query.exec("SELECT _id, Name, Age FROM People");

    //Выводим значения из запроса
    while (query.next())
    {
    QString _id = query.value(0).toString();
    QString Name = query.value(1).toString();
    QString Age = query.value(2).toString();
    ui->textEdit->insertPlainText(_id+" "+Name+" "+Age+"\n");
    }
}


MainWindow::~MainWindow()
{
    delete ui;
}

Answer 1

https://translate.google.ru/

Answer 2

Read the documentation , or at worst any Qt tutorial.