Selecting data from mysql using qt?

tony · wrote on 11 Oct 2010, 17:33

Did you leave

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

commented?

doforumda · wrote on 11 Oct 2010, 17:36

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 · wrote on 11 Oct 2010, 17:37

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

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

commented?[/quote]

Dmytro · wrote on 11 Oct 2010, 17:39

Try uncomment line 23

doforumda · wrote on 11 Oct 2010, 17:42

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 · wrote on 11 Oct 2010, 17:55

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

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

doforumda · wrote on 11 Oct 2010, 18:01

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 · wrote on 11 Oct 2010, 18:05

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

Dmytro · wrote on 11 Oct 2010, 18:12

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 · wrote on 11 Oct 2010, 18:16

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 · wrote on 11 Oct 2010, 18:32

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

doforumda · wrote on 11 Oct 2010, 18:34

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

doforumda · wrote on 11 Oct 2010, 19:14

anyone who can help?

Dmytro · wrote on 11 Oct 2010, 19:30

!http://hin.dp.ua/files/down/qt_scr.PNG(my screenshot)!

doforumda · wrote on 11 Oct 2010, 19:56

well i dont have that option. here is what i get
when i click file/new file or project then this screenshot
"Your text to link here...":http://www.freeimagehosting.net/uploads/702f633ae7.png
then i keep clicking next getting the follwoing screenshots
"Your text to link here...":http://www.freeimagehosting.net/uploads/ab872acfb8.png
"Your text to link here...":http://www.freeimagehosting.net/uploads/45c51ab364.png
"Your text to link here...":http://www.freeimagehosting.net/uploads/84605eae46.png
"Your text to link here...":http://www.freeimagehosting.net/uploads/84605eae46.png

Dii · wrote on 11 Oct 2010, 21:47

Well, it should make no problem to have SQL query before exec(), at least I don't have any problem with that.

Let's get back to square one:
You said if you uncomment the
@bool ok = db.open();@
then your program hangs. Can we see the value of 'ok'?
@qDebug() << ok;@
My guess is probably you have problems granting the rights in mysql when you've created the table... have you made
@GRANT ALL ON testTwo.* to 'root'at'localhost' IDENTIFIED BY 'somepassword';@
(Ouch please replace the 'at' with the 'at' sign, the forum motor uses it for code tags, I don't know how to write it... I hope it's not confusing.
I'm not sure if you can do it with empty password, I guess yes, but I never do that.)

doforumda · wrote on 12 Oct 2010, 05:49

i now put password for root at localhost.
when i place qDebug() << ok then it displays this
@
false
QSqlQuery::exec: database not open
@

false might be the value of ok.

lyuts · wrote on 12 Oct 2010, 08:16

Are you able to connect to your DB from shell?

doforumda · wrote on 12 Oct 2010, 08:21

i dont know how to connect to my DB from shell. I install xampp which is easy for me to manage my databases.
how can i connect from shell?

lyuts · wrote on 12 Oct 2010, 08:25

@mysql -h host -D dbname -u user@

I guess your can omit host parameter if you are connecting to localhost. You might need to specify "-p password" switch also (depends on mysql configuration).