MySQL query

SGaist

Hi,

A select query that returns nothing is likely what you want to check.

What exactly is your issue with that ?

One tip, if you only want to check that it exists, no need to query the content of the whole table, only the field you are interested in is enough.

Kent-Dorfman

In addition to what @SGaist suggested you can make the database table use a unique key on the data fields being inserted. That way if you try to insert the same data more than once the transaction will fail. At least that is the strategy I do in PostgreSQL. I assume unique keys are supported in mySQL.

Xmodpt

hello @SGaist and @Kent-Dorfman

I am realy sorry but i have pasted the wrong query....
the correct one is

candidate_query := SELECT domain FROM candidates WHERE domain = :d;

It seems that i haven't explain my self correctly

the intent is not to "input" data into the table but read from data from it.

in a nut shell....

Camera reads plate -> check if plate exists in DB -> if exists... shows a Warning Message that includes the detected plate + custom text... if not... keep reading.

NOTE: the data in the database is a user input process via a dashboard manualy.

Hope'd i was able to clarify my questions....

regards
NP

Kent-Dorfman

then simply write a query looking for that license number. If the number of rows returned equals zero then it was not found. pretty simple...

Xmodpt

the question is how do i put it in C++ and in my UI form to echo the output

VRonin

QSqlQuery query;
query.prepare("SELECT domain FROM candidates WHERE domain = :d");
query.bindValue(":d", domain);
if(!query.exec())
qDebug() << "Unable to execute query";
if(query.next()){
qDebug() << "The domain is already in the database";
}

shows a Warning Message

https://doc.qt.io/qt-5/qmessagebox.html#warning

Xmodpt

@VRonin

Thank you for your help. I will test it tomorrow and I'll let you know.

Ps- in order the get the warning to work on my UI all I need is to change from qdebug to ui->

Thank you
Np

Xmodpt

@VRonin

Hello m8

It worked like a charm... thank you very much for the tip.

Let me ask you guys a tip:

I have made some changes but what i need to get the a custom output in the QMessageBox. something like

"Warning: XX@@ZZ (domain VAR) plate is blacklisted!"

is there a way to output my (domain) var in the QMessageBox ?

My current code:


    QSqlQuery query;
    query.prepare("SELECT domain FROM candidates WHERE domain = :d");
    query.bindValue(":d", domain);
    if(!query.exec())
    qDebug() << "Unable to execute query";
    if(query.next()){
    qDebug() << "The domain is already in the database";
        QMessageBox msgBox;
        QPixmap myIcon(":/images/danger.png");
        msgBox.setIconPixmap(myIcon);
        msgBox.setText("PLATE IS BLACKLISTED.");
        msgBox.exec();

Also i have tried using a UI Form but i was unable to print my "domain" value output

//////// UI FORM - msgbox.ui///////

      MsgBox msgbox;
       msgbox.setModal(true);
       msgbox.exec();

///////////////////////////////////////////////////////////////////////////////////

Kind Regards
Xmodpt

VRonin

msgBox.setText(QStringLiteral("%1 PLATE IS BLACKLISTED.").arg(domain));

Xmodpt

@VRonin

Hello m8

Thankyou verry much for all your help.
ALL is working like it should thanks to you.

Until next time
Xmodpt