QT SQL DATABASE LOGIN

GREYON

hello, am new in application development.
I have connected my application to sql database and am able to enter data into the database through the user interface. But I want to make sure that a user does not enter same type of data twice.I have tried to use the if and the else statement,but the problem is that the else is not working, what could be the problem? I will appreciate your help. below is the code:```
#include "schoolfee.h"
#include "ui_schoolfee.h"

schoolFee::schoolFee(QWidget *parent) :
QDialog(parent),
ui(new Ui::schoolFee)
{
ui->setupUi(this);
ui->SURNAME->setPlaceholderText("ENTER SURNAME");
ui->GRADE->setPlaceholderText("INTER GRADE, e.g 9");
ui->CLASS->setPlaceholderText("ENTER CLASS e.g 9A");
ui->AMOUNT->setPlaceholderText("ENTER AMOUNT e.g 100");
ui->OTHERNAME->setPlaceholderText("ENTER OTHER NAME(S)");
//ui->DATE->setPlaceholderText("e.g 01/01/2000");

}

schoolFee::~schoolFee()
{
delete ui;

}

void schoolFee::on_ENTER_FEE_clicked()
{

QString name =ui->SURNAME->text();
QString grade =ui->GRADE->text();
QString clas= ui->CLASS->text();
QString amount=ui->AMOUNT->text();
QString receiver=ui->OTHERNAME->text();
QString date=ui->DATE->text();



if(name=="" || grade==""|| clas==""||amount==""||receiver==""||date=="")
{

  QMessageBox::warning(this,"warning","PLEASE ENTER ALL THE REQUIRED DETAILS");
}
else
  {

QSqlDatabase::database();
QSqlQuery query;
query.prepare(QString("SELECT SURNAME,LASTNAME FROM payments WHERE SURNAME=:SURNAME AND LASTNAME=:LASTNAME"));

query.bindValue(":SURNAME",name);
query.bindValue(":LASTNAME",receiver);

if(!query.exec()){

     QMessageBox::warning(this,"warninng","PLEASE TURN ON THE SYSTEM!");

}
else
{

while(query.next())
{
QString nameFromDB=query.value(0).toString();
QString receiverFromDB=query.value(1).toString();

  if(nameFromDB==name && receiverFromDB==receiver){

      QMessageBox::warning(this,"WARNING","THE NAME HAS BEEN ENTERED ALREADY!!!\n"
           " USE INITIAL IF ITS A DIFFERENT NAME");
                        break;
            }
       else
     {
 


    QSqlQuery qry;

qry.prepare("INSERT INTO payments (SURNAME,LASTNAME,GRADE,CLASS,AMOUNT,DATE)"
            "VALUES(:SURNAME, :LASTNAME, :GRADE, :CLASS, :AMOUNT,  :DATE)");

qry.bindValue(":SURNAME",name);
qry.bindValue(":GRADE",grade);
qry.bindValue(":CLASS",clas);
qry.bindValue(":AMOUNT",amount);
qry.bindValue(":LASTNAME",receiver);
qry.bindValue(":DATE",date);

if(qry.exec())
    {
   QMessageBox::information(this,"inserted","PAYMENTS RECORDED SUCCESSFULLY!");

  }
else

{

   QMessageBox::warning(this,"warning","PAYMENT NOT RECORDED!");

}
}
}
}
}

}

GREYON

@Christian-Ehrlicher
Okay , thanks for the information,but am new here,how can it mark as solved please?

JonB

This post is deleted!

JonB

@GREYON said in QT SQL DATABASE LOGIN:

the problem is that the else is not working, what could be the problem?

Hi & welcome.

Which else, and what does "not working" mean, what happens that should not?

GREYON

This part:```
else
{

    QSqlQuery qry;

qry.prepare("INSERT INTO payments (SURNAME,LASTNAME,GRADE,CLASS,AMOUNT,DATE)"
            "VALUES(:SURNAME, :LASTNAME, :GRADE, :CLASS, :AMOUNT,  :DATE)");

qry.bindValue(":SURNAME",name);
qry.bindValue(":GRADE",grade);
qry.bindValue(":CLASS",clas);
qry.bindValue(":AMOUNT",amount);
qry.bindValue(":LASTNAME",receiver);
qry.bindValue(":DATE",date);

if(qry.exec())
    {
   QMessageBox::information(this,"inserted","PAYMENTS RECORDED SUCCESSFULLY!");

  }
else

{

   QMessageBox::warning(this,"warning","PAYMENT NOT RECORDED!");

}
}
}
}
}

GREYON

The main aim is prevent the user from entering the same **SURNAME and LASTNAME twice, those line of code I wanted them to be executed if the data entered does not match ant any of the data already in the data base .but instead its not responding

SGaist

Hi,

That's the kind of constraints that should be done at the database level.
Your database structure might also be too simple in the sense that if can be pretty easy to get duplicated data with small typos.

JonB

@GREYON
You should say what goes wrong? Do you get a compilation error? A runtime error? A message? If so, tell us what the message is. Something doesn't do what you expect? If so what, and how do you know? That's what's required for people to look at your issue!

qry.prepare("INSERT INTO payments (SURNAME,LASTNAME,GRADE,CLASS,AMOUNT,DATE)"
            "VALUES(:SURNAME, :LASTNAME, :GRADE, :CLASS, :AMOUNT,  :DATE)");

Those two strings get joined. Look at them, and you will realize that will generate in the middle:

... CLASS,AMOUNT,DATE)VALUES(:SURNAME,

The VALUES touches the parenthesis to its left, which is different from the sample code at https://doc.qt.io/qt-5/qsqlquery.html#approaches-to-binding-values. I don't know if that will be enough to error.

In any case, when a query goes wrong (if that's what's happening), use https://doc.qt.io/qt-5/qsqlquery.html#lastError to print out the text of the error.

GREYON

@SGaist
Now what are you suggesting items of help?

JonB

@GREYON

In any case, when a query goes wrong (if that's what's happening), use https://doc.qt.io/qt-5/qsqlquery.html#lastError to print out the text of the error.

Have you done this yet?

GREYON

@JonB
Not yet,thanks let me go through it

SGaist

@GREYON said in QT SQL DATABASE LOGIN:

@SGaist
Now what are you suggesting items of help?

What experience do you have with relational database design ?

GREYON

@SGaist
Not as experience as such,we let about it ,it was part of our course now we have a project.

SGaist

Well, in that case you should start by learning a bit more about them before going further. At least take the time to go through Qt's SQL module documentation and examples.

GREYON

@SGaist
Yeah,I think so

GREYON

@GREYON
Thanks after going through Qsql documentation,the problem has been resolved

Christian Ehrlicher

@GREYON Then please mark this topic as solved, thx.

GREYON

@Christian-Ehrlicher
Okay , thanks for the information,but am new here,how can it mark as solved please?