How to declare a negative number on a QTableView using SQlite - sqlite

Question

I am designing a major user interface with several fields.
In order to shrink the problem I created a small minimal application with 5 columns: name, image, dataDatabase, dateTime and coordNumber.
I have a MainWindow with a QTableView, as soon as I right click inside the QTableView an AddItemDialog opens up with:
1) nameLineEdit
2) ImLineEdit
3) imageLineEdit
4) dateTimeEdit
5) numLineEdit
The issue that I have is that I can't find a way to accept the 5) numLineEdit through the AddItemDialog when the number is negative.
Currently it only saves positive numbers. How to handle this exception?
I read from official document but I could not figure out. However always from this official source it seems that a negative number must be interpreted as "no limit" value. The explanation was short and didn't provide any useful small example, so I am still not sure how to proceed.
I am including the most important parts of the application below with the related description of the procedure I followed:
I created an Item with the fields item.h:
class Item
{
public:
Item(const double dateTime,
const QString &name = "", const QString &image = "",
int num, const QByteArray &imagesData = QByteArray());
QString name() const { return mName; }
QString image() const { return mImage; }
QByteArray imagesData() const { return mImagesData; }
double dateTime() const { return mDateTime; }
int num() const { return mNumberCoord; }
private:
QString mName;
QString mImage;
QByteArray mImagesData;
double mDateTime;
int mNumberCoord
};
and its related item.cpp
Item::Item(const double dateTime, int num,
const QString &name, const QString &image, int num,
const QByteArray &imagesData) :
mName(name),
mImage(image),
mImagesData(imagesData),
mDateTime(dateTime),
mNumberCoord(num)
{
}
I created a database.h table that will contain the parameters as follows:
class dataBase : public QObject
{
Q_OBJECT
public:
explicit dataBase(QObject *parent = nullptr);
bool inizializationDataBase(const QString &nameDataBase);
bool configureDataBase();
QString getError() const { return mError; }
bool addItem(const Item &item);
private:
QSqlDatabase mDatabase;
QString mError;
};
And its related database.cpp file - I am only including the most important piece of the code for this file:
#define CREATE_TABLE \
" CREATE TABLE IF NOT EXISTS Fish_Table" \
" (id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL" \
", name TEXT NOT NULL" \
", image TEXT NOT NULL" \
", dataDataBase BLOB NOT NULL" \
", dateTime DOUBLE NOT NULL" \
", num INTEGER NOT NULL)"
dataBase::dataBase(QObject *parent) : QObject(parent)
{
}
bool dataBase::addItem(const Item &item) {
QSqlQuery q;
q.prepare("INSERT INTO Fish_Table (name, image, dataDatabase, dateTime, num) VALUES (?,?,?,?,?)");
q.addBindValue(item.name());
q.addBindValue(item.image());
q.addBindValue(item.imagesData());
q.addBindValue(item.dateTime());
q.addBindValue(item.num());
bool ok = q.exec();
if (!ok) {
mError = q.lastError().text();
}
return ok;
}
and finally the AddItemDialog.cpp that contains the fields I am trying to pass to the QTableView of the MainWindow.
AddItemDialog.cpp
void AddItemDialog::on_buttonBox_accepted()
{
QFile dataBase(ui->imageLineEdit->text());
if (!dataBase.open(QIODevice::ReadOnly)) {
QMessageBox::critical(this, "Error", dataBase.errorString());
return;
}
mItem = Item(ui->dateTimeEdit->dateTime(),
ui->nameLineEdit->text(),
ui->ImLineEdit->text(),
ui->numLineEdit->text(),
dataBase.readAll());
dataBase.close();
accept();
}
I expect to save either positive or negative numbers on the QTableView, but as of now I can only save positive numbers. How to handle this exception?

Answer 1

So the answer is yes, it is possible to handle negative numbers. For some reasons I thought that SQL was not able to do that but below is a small example of how to handle that exception:
#define CREATE_TABLE \
" CREATE TABLE IF NOT EXISTS Fish_Table" \
" (id INTEGER PRIMARY KEY AUTOINCREMENT NOT NULL" \
", name TEXT NOT NULL" \
", image TEXT NOT NULL" \
", dataDataBase BLOB NOT NULL" \
", dateTime DOUBLE NOT NULL" \
", num INTEGER NOT NULL)"
dataBase::dataBase(QObject *parent) : QObject(parent)
{
}
bool dataBase::addItem(const Item &item) {
QSqlQuery q;
q.prepare("INSERT INTO Fish_Table (name, image, dataDatabase, dateTime, num) VALUES (name,descriptionOfImage,BLOB(actual image), put date&time,-200)");
q.addBindValue(item.name());
q.addBindValue(item.image());
q.addBindValue(item.imagesData());
q.addBindValue(item.dateTime());
q.addBindValue(item.num());
bool ok = q.exec();
if (!ok) {
mError = q.lastError().text();
}
return ok;
}
This is also a very valuable source.
If also there is any need to turn a positive number into a negative number than this is a possible solution:
UPDATE Table
SET field= (field * -1)
Where SIGN(field) = -1
Also this is very useful in case someone needs the SQL code for an additional source.