I connect in the database but the values do not change when I give UPDATE MYSQL Qt C ++

Question

I connect in the database but the values do not change when I give UPDATE MYSQL Qt C ++

Navigation

#1 by (1 votes)
#2 by (0 votes)

0

The data is loaded into the table, so I change the data in the table, when I click the button to update, I get the data (even the changes) and save it to the variable, but it seems that when I enter the sql query nothing happens . I need to be able to update the table data as soon as I change something and click the refresh button.

Connection to the bank (ok):

void ConectaBanco()
{
    //Variavel do tipo DataBase
    QSqlDatabase db;

    //Conexao com o MYSQL
    db = QSqlDatabase::addDatabase("QMYSQL");

    //Servidor que vai receber o DB (padrão do server local)
    db.setHostName("127.0.0.1");

    //Porta que vai conectar com o DB (por padrão vai ser 3306)
    db.setPort(3306);

    //Seleciona o banco de dados
    db.setDatabaseName("cursos");

    //Usuario do BD
    db.setUserName("root");

    //Caso tenha senha no mysql
    //db.setPassword();

    //Teste de conexao
    if(db.open())
    {
        qDebug()<<"Sucesso ao abrir a conexão";
    }
    else
    {
        qDebug()<<db.lastError().text();
    }
}

Update function:

void MainWindow::on_pushButton_clicked()
{
    int fila = 0;
    ConectaBanco();
    int CdAluno = ui->tabelaCarga->model()->data(ui->tabelaCarga->model()->index(fila,0)).toInt();
    QString NmAluno = ui->tabelaCarga->model()->data(ui->tabelaCarga->model()->index(fila,1)).toString();
    QString NmCurso = ui->tabelaCarga->model()->data(ui->tabelaCarga->model()->index(fila,2)).toString();
    QString NmEscola = ui->tabelaCarga->model()->data(ui->tabelaCarga->model()->index(fila,3)).toString();


    QSqlQuery query("UPDATE matricula set NmAluno= '"+NmAluno+"', "
                                         "NmCurso= '"+NmCurso+"', "
                                         "NmEscola='"+NmEscola+"' "
                                         "WHERE CdMatricula='"+CdAluno+"'");
    query.exec();

}

When I debug and place the mouse over the UPDATE string, the following message appears: no much value

I would like to know how to solve the problem and be able to change the data perfectly.

mysql c++ qt crud qtgui

asked by anonymous 08.06.2017 / 12:51

2 answers

1

Instead of concatenating the query string, try something like this:

#include <QVariant>
...
...

QSqlQuery query
query.prepare("UPDATE matricula SET NmAluno= ?, NmCurso= ?, NmEscola=? WHERE CdMatricula=?");

query.addBindValue(NmAluno);
query.addBindValue(NmCurso);
query.addBindValue(NmEscola);
query.addBindValue(CdAluno);

if( ! query.exec()) {
    qDebug() << "Erro ao executar query!!";
}

And be careful, what's in your void ConectaBanco() method can only run once. If you add a DB twice, you'll get a duplicate connection error (as it's popping up on your Qt Creator output screen) and your code may not work as you expect it to. If I were you, I would create an auxiliary class to handle connections to MySql.

10.06.2017 / 15:37

Comparing dates [duplicate] DASHBOARD - Can you export to the Browser ?! (Any language for the web) [closed]

score 0 · Accepted Answer

The update function should be with the CdMatricula field in the format string for the query to recognize the code:

void MainWindow::on_pushButton_clicked()
{
    ConectaBanco();
    int linha = 0;
    QString CdAluno = ui->tabelaCarga->model()->data(ui->tabelaCarga->model()->index(linha,0)).toString();
    QString NmAluno = ui->tabelaCarga->model()->data(ui->tabelaCarga->model()->index(linha,1)).toString();
    QString NmCurso = ui->tabelaCarga->model()->data(ui->tabelaCarga->model()->index(linha,2)).toString();
    QString NmEscola = ui->tabelaCarga->model()->data(ui->tabelaCarga->model()->index(linha,3)).toString();

    qDebug()<<CdAluno<<NmAluno<<NmCurso<<NmEscola;

    QSqlQuery query;

    query.prepare("UPDATE 'matricula' SET 'NmAluno' = '"+NmAluno+"', "
                                         "'NmCurso' = '"+NmCurso+"', "
                                         "'NmEscola' = '"+NmEscola+"'"
                                         " WHERE 'matricula'.'CdMatricula' = '"+CdAluno+"'");



    if(query.exec())
    {
        qDebug()<<"Query executada com sucesso!";
    }
    else
    {
        qDebug()<<"Erro ao executar a query";
    }

    //atualiza a tabela automaticamente
    on_btnCarga_clicked();
}