Qt - QSql Unable to fetch row, no query on attempt to insert

Question

I'm trying to insert data into a table. Here's the code:

void AddContacts::saveContact() {

    QString first_name = ui->lineFirstName->text();
    QString last_name = ui->lineLastName->text();
    QString street_address = ui->lineStreetAddress->text();
    QString city = ui->lineCity->text();
    QString state = ui->comboBoxState->currentText();
    QString zip_code = ui->lineZip->text();
    QString personal_email = ui->linePersonalEmail->text();
    QString work_email = ui->lineWorkEmail->text();
    QString home_phone = ui->lineHomePhone->text();
    QString cellular_phone = ui->lineCellularPhone->text();
    QString work_phone = ui->lineWorkPhone->text();
    QString pager = ui->linePager->text();
    QString facebook = ui->lineFacebook->text();
    QString twitter = ui->lineTwitter->text();
    QString notes = ui->textEditNotes->toPlainText();

    // Insert into the database
    QSqlDatabase db = QSqlDatabase::addDatabase("QSQLITE");
    db.setDatabaseName("db.db3");
    db.open();

    QSqlQuery qry;
    QString query = "INSERT INTO (id, first_name, last_name, street_address, city, state, zip_code, personal_email, work_email, home_phone, cellular_phone, work_phone, pager, facebook, twitter, notes) VALUES('null','" + first_name + "','" + last_name +"','" + street_address + "','" + city + "','" + state + "','" + zip_code + "','" + personal_email + "','" + work_email + "','" + home_phone + "','" + cellular_phone + "','" + work_phone + "','" + pager + "','" + facebook + "','" + twitter + "', '" + notes + "')";
    qry.prepare(query);

    if(!qry.exec()) {
        qDebug() << qry.lastError();
    }
    else {
        qDebug() << "Success!";
    }

Here is what I used to create the table:

CREATE TABLE contacts (
id int primary key,
first_name varchar(20),
last_name varchar(20),
street_address text,
city varchar(30),
state varchar(20),
zip_code varchar(10),
personal_email varchar(40),
work_email varchar(40),
home_phone varchar(12),
cellular_phone varchar(12),
work_phone varchar(12),
pager varchar(12),
facebook text,
twitter varchar(20),
notes text);

I'm getting this error:

QSqlError(-1, "Unable to fetch row", "No query")

I'm not sure what I could be doing wrong. Can you find anything?

Answer 1

Don't insert a string 'null' as a value for column id. Use a valid integer instead. If you really want the first row to have a NULL id, the SQL statement looks like this ... VALUES (NULL, ....

Your code is very prone to errors since you don't escape apostrophes in your input. If some of your text fields contain a ', your SQL statement will fail. You should bind your columns to variables. This is from the Qt references and you should use this approach:

 QSqlQuery query;
 query.prepare("INSERT INTO contacts (id, first_name, last_name) "
               "VALUES (:id, :first_name, :last_name)");
 query.bindValue(":id", 1001);
 query.bindValue(":first_name", first_name);
 query.bindValue(":last_name", last_name);
 query.exec();