Selecting data from mysql using qt?

? Offline

Line no. 22 and 23, can just be replaced with ...

@
QSqlQuery query("SELECT * FROM testTable");
@

But also, do check the documentation for QSqlQuery, where it is recomended NOT to use SELECT *

doforumda

now i changed it to this
@
query.exec("SELECT firstname,lastname FROM testTable");
@
still the same errors

and i am following this link "Your text to link here...":http://doc.trolltech.com/4.7/sql-sqlstatements.html

tony

Maybe an "#include <QVariant>" is missing at the top?

T.

MTK358

Why not just

@#include <QtCore>
#include <QtSql>@

and not worry about every single class you use?

tony

That can be a solution only when you're testing something. So, in this case, I agree with you, let's avoid such worries.

But if your project grows up, it's better to include what's needed, otherwise your compilation time can increase a lot.

T.

doforumda

i add #include <QVariant>

now it is saying
@
QSqlQuery::exec: database not open
@

Dmytro

Try to use QSqlQuery::lastError() for find problem

doforumda

what is the problem now in my code why it is not opening database?

tony

Did you leave

@
//bool ok = db.open();
@

commented?

doforumda

well i changed my code to this and added lastError as well

@
#include <QApplication>
#include <QSqlDatabase>
#include <QSqlError>
#include <QSqlQuery>
#include <QDebug>
#include <QString>
#include <QVariant>
//#include <QtCore>
//#include <QtSql>
//#include "../connection.h"
#include "db.h"

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setDatabaseName("testTwo");
db.setUserName("root");
db.setPassword("");
db.setHostName("localhost");

//bool ok = db.open();

QSqlQuery query;
query.exec&#40;"SELECT firstname,lastname FROM testTable"&#41;;
while(query.next()) {
    QString firstName = query.value(0).toString();
    QString secondName = query.value(1).toString();
    qDebug() << "First Name: " << firstName << "Last Name:" << secondName;
    qDebug() << db.lastError();
}
return a.exec&#40;&#41;;

}
@

it still says QSqlQuery::exec: database not open

doforumda

it is still as commented
[quote author="Antonio Di Monaco" date="1286818410"]Did you leave

@
//bool ok = db.open();
@

commented?[/quote]

Dmytro

Try uncomment line 23

doforumda

i uncomment line 23 and comment everything below line 23 then it just says
@
Starting /home/zafar/c++/dbExample-build-desktop/dbExample...
@

and stucks there

Dmytro

OH! You use SQL code before
a.exec()
!
Are you sure?

Create standart QT GUI application and wrote sql code in mainwindow module.

doforumda

i am new to qt. how can i create Qt Gui App and do you mean i should write sql code in mainwindow.h file?

doforumda

right now i have three files. db.h, db,cpp and main.cpp

Dmytro

Run QT Creator.
Use menu File/new file or project.
Select QT Gui application.
...
and select SQL checkbox
...
and write sql code in MainWindow.cpp
...
and see SQL Example please

doforumda

well i tried "File/new file or project and select qt gui app" but i ddint find any sql checkbox anywhere in creating new project

Dmytro

no coments...
How can I send you screenshot?

doforumda

you can add pictures here as screenshots or if you want my email address i ll give you that as well for screenshots