Basic qt with mysql?

doforumda

hi

i install qt creator then mysql driver for qt and then i install xampp to make databases for qt. Now i want to access data in database using qt. i am following this link but it is not working for me. "Your text to link here...":http://doc.trolltech.com/3.0/sql.html

then problem is when i type the same code
@
#include <QApplication>
#include <QSqlDatabase>

int main( int argc, char *argv[] )
{
    QApplication app( argc, argv );

    QSqlDatabase *defaultDB = QSqlDatabase::addDatabase( QMYSQL );
    if ( ! defaultDB ) {
        qWarning( "Failed to connect to the database driver" );
        return 1;
    }
    defaultDB->setDatabaseName( "testTwo" );
    defaultDB->setUserName( "root" );
    defaultDB->setPassword( "" );
    defaultDB->setHostName( "localhost" );

    if ( defaultDB->open() ) {
        // Database successfully opened; we can now issue SQL commands.
    }

    return 0;
}

@

then it returns these errors
@
QSqlDatabase: No such file or directory main.cpp 2
QSqlDatabase was not declare in this scope main.cpp 9
defaultDB was not declare in this scope main.cpp 9
QSqlDatabase is not a class or namespace main.cpp 9
QMYSQL was not declare in this scope main.cpp 9
@

how can i access data from my database table?
other thing is i am using xampp for creating mysql databases. when i make database it is placed in this directory opt/lampp/var/mysql/testTwo.

vsorokin

in .pro file you should add
@QT += sql@

doforumda

now it displays this error
@
in function int main(int, char**)
cannot convert to QSqlDatabase to QSqlDatabase in inititalization main.cpp 9
@

Zlatomir

That's because you assign QSqlDatabase *defaultDB ( a pointer) with what "addDatabase(...)":http://doc.qt.nokia.com/4.6/qsqldatabase.html#addDatabase returns (a QSqlDatabase, not a pointer to QSqlDatabase)

doforumda

so i should use something like this QSqlDatabase defaultDB = QSqlDatabase::addDatabase("QMYSQL");

DenisKormalev

Yes. And in case of one db without name (i.e. default database) you don't need to provide it to QSqlQuery.

doforumda

now it displays this error
@
in function int main(int, chat**)
no match for operator! in !db
candidates are operator!(bool) <built-in>
@

Zlatomir

You can use "isValid()":http://doc.qt.nokia.com/4.6/qsqldatabase.html#isValid

doforumda

now it is saying
@
QSqlDatabase: QMysql driver is not loaded
QSqlDatabase: available drivers :QSQLITE QSQLITE2
@

i have installed Mysql driver here "Your text to link here...":http://developer.qt.nokia.com/forums/viewthread/1121/P30/

DenisKormalev

It says that something is wrong with your mysql plugin. What do you have in your plugins/sqldrivers folder?

doforumda

i have 10 different folders and four files. files with names are libqsqlmysql.so, qsqldriverbase.pri, readme, sqldriver.pro

doforumda

i also run this code
@
#include <QCoreApplication>
#include <QSqlDatabase>
#include <QSqlError>
#include <QStringList>
#include <QtDebug>

  int main( int argc, char *argv )
  {
  QCoreApplication app( argc, argv );
  qDebug() << QSqlDatabase::drivers();
  }

@

it displays this
@
("QSQLITE","QSQLITE2")
@

DenisKormalev

Not folder with plugin sources, but folder with qt plugin binaries. It is folder named plugins/sqldrivers in root of your Qt folder.

doforumda

well i checked this in this path home/qtsdk-2010.05/qt/src/plugins/sqldrivers

I have two plugins folders. one in home/qtsdk-2010.05/qt/plugins
in this plugin folder i have 11 folders with one named sqldrivers. inside this sqldriver folder i have these 3 files "libqsqlite.so, libqsqlite2.so, libqsqlpsql.so"

the other is mentioned above which inside src.

DenisKormalev

Put mysql plugin in this folder.

doforumda

from which folder i can get mysql plugin and what is the name of that mysql plugin? you mean this one libqsqlmysql.so which is in src/plugins/sqldrivers/mysql folder?

DenisKormalev

yes