Selecting data from mysql using qt?

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

doforumda

anyone who can help?

Dmytro

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

doforumda

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

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

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

Are you able to connect to your DB from shell?

doforumda

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

@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).

doforumda

i think i did not install any mysql client. bcause it displays this output
@
root@zafar-laptop:/# mysql -h localhost -D testTwo -u root -p xxxxxx
The program 'mysql' can be found in the following packages:

mysql-client-core-5.1
mysql-client-5.0
mysql-cluster-client-5.1
Try: apt-get install <selected package>
@

lyuts

Run
@dpkg --list | grep mysql@
and post the output for this command.

doforumda

here it is
@
root@zafar-laptop:/# dpkg --list | grep mysql
ii libmysqlclient-dev 5.1.41-3ubuntu12.6 MySQL database development files
ii libmysqlclient16 5.1.41-3ubuntu12.6 MySQL database client library
ii mysql-common 5.1.41-3ubuntu12.6 MySQL database common files (e.g. /etc/mysql

@

lyuts

How did you create your database? I don't see any mysql server either.

doforumda

well i download xampp and install it. i created database using phpmyadmin.

doforumda

i install xampp in this folder /opt/lampp

and my database is in /opt/lampp/var/mysql

lyuts

Ok, I see. What is the location of your XAMPP installation? try to find the mysql binary there. And use the whole path (since I assume it is not in PATH) when connecting, i.e.

@/path/to/xampp/bin/mysql -D dbname -u username@

UPD: Didn't notice the location of xampp. then try (I guess it would be like this) @/opt/lampp/bin/mysql@

doforumda

now here it what it says
@
root@zafar-laptop:/# /opt/lampp/bin/mysql -D testTwo -h localhost -u root -p 123456
Enter password:
ERROR 1049 (42000): Unknown database '123456'
@
i am providing the right pw

lyuts

Try not passing -p switch. I guess you will be prompted to type in your password.
or
@/opt/lampp/bin/mysql -u root testTwo@

doforumda

now it output is Access Denied
@
root@zafar-laptop:/# /opt/lampp/bin/mysql -u root testTwo
ERROR 1045 (28000): Access denied for user 'root'at'localhost' (using password: NO)
@

lyuts

I'm sorry i just confused you with my last post.

@/opt/lampp/bin/mysql -u root -p 123456 testTwo@

I thought that mysql would prompt you but it didn't.

Dii

Do it this way, then it will prompt for a password:

@/opt/lampp/bin/mysql -D testTwo -h localhost -u root -p
@

doforumda

i got a big ouput here but i have not seen any errors in this. when i try to post whole output this forum didnt allow me to post more than 6000 characters

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Selecting data from mysql using qt?