getting MySQL to work with Qt

[Ashish]

Hi,

I have been trying to get Qt to work with MySQL without any luck. When I run a 2 line test code, it comes back with a message saying- "This application has failed to start because LIBMYSQL.DLL was not found. Re-installing the application may fix this problem". Can anyone please guide me on fixing the issue and getting MySQL to work with Qt?

Here's what I have done so far-

1) I downloaded and installed MySQL 5.1.34 using the installer( mysql-5.1.34-win32.msi) from MySQL website.
2) I downloaded the latest opensource Qt sources(qt-win-opensource-src-4.5.1) from Qt website and configured it as follows:
a) added the path to locate qmake etc.
b). configure -debug-and-release -l libmysql -I D:\MySQL\MySQLServer5.1\include -L D:\MySQL\MySQLServer5.1\lib\opt -qt-sql-mysql -qt-sql-odbc
c) nmake

These steps went fine but when I run the test code, it doesn't work. The code that I was trying to run is :
------

#include <QCoreApplication>
#include <QSqlDatabase>
#include <QStringList>
#include <QtDebug>
 
int main( int argc, char **argv )
{
   QCoreApplication app( argc, argv );
   qDebug() << QSqlDatabase::drivers();
}

#include <QCoreApplication>
#include <QSqlDatabase>
#include <QStringList>
#include <QtDebug>
 
int main( int argc, char **argv )
{
   QCoreApplication app( argc, argv );
   qDebug() << QSqlDatabase::drivers();
}

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------

Can anyone please help me fix the issues here?

Thanks,
Ashish

[wysota]

Where did you place the MySQL dll? It should be in a folder that is in your system search path (i.e. C:\Windows\system32) so that the system dynamic linker can find it. You can also place it alongside your application binary as its directory is also searched by the linker.

[Ashish]

Hi Wysota,

Thanks for replying.

Are you talking about libmysql.dll? I cannot find any file by the name MYSQL.dll.

I did not place the 'libmysql.dll' anywhere, they are presently located in the MySql installation folder at "../MySQL/MySQLServer5.1/bin", "../MySQL/MySQLServer5.1/lib/debug" and "../MySQL/MySQLServer5.1/lib/opt"

Is there any other step that I need to do after the (1) Qt configure step as per my previous post and (2) nmake?

Thanks,
Ashish

[wysota]

They have to be accessible by the compiler and linker. Try placing the library in C:\Windows\System32 and see if it helps.

[Ashish]

Thanks Wysota. I placed the DLL library in my application directory and it works now.

The code from my first post works and gives me the following result:

("QMYSQL3", "QMYSQL", "QODBC3", "QODBC", "QSQLITE")
Press any key to continue . . .

However when I add a few more lines to my code to open a test database it doesn't work. Here is the new code:
-----

#include <QCoreApplication>
#include <QSqlDatabase>
#include <QStringList>
#include <QtDebug>
#include <QPushButton>
#include <QApplication>
#include <QSqlError>
#include <QSqlQuery>
 
#include <iostream>
 using namespace std;
int main( int argc, char **argv )
{
 
       QCoreApplication app( argc, argv );
       qDebug() << QSqlDatabase::drivers();
 
       QSqlDatabase *mydb = new QSqlDatabase();
       mydb->addDatabase("QMYSQL");
	mydb->setHostName("w.x.y.z"); //number changed
	mydb->setPort(zzzz); //number changed
	mydb->setDatabaseName("test");
	mydb->setUserName("tmp");
	mydb->setPassword("tmp123");
	bool ok = mydb->open();
	qDebug()<<mydb->lastError();	
	 cout<<"ok="<<ok<<endl;
 
}

#include <QCoreApplication>
#include <QSqlDatabase>
#include <QStringList>
#include <QtDebug>
#include <QPushButton>
#include <QApplication>
#include <QSqlError>
#include <QSqlQuery>

#include <iostream>
 using namespace std;
int main( int argc, char **argv )
{

       QCoreApplication app( argc, argv );
       qDebug() << QSqlDatabase::drivers();

       QSqlDatabase *mydb = new QSqlDatabase();
       mydb->addDatabase("QMYSQL");
	mydb->setHostName("w.x.y.z"); //number changed
	mydb->setPort(zzzz); //number changed
	mydb->setDatabaseName("test");
	mydb->setUserName("tmp");
	mydb->setPassword("tmp123");
	bool ok = mydb->open();
	qDebug()<<mydb->lastError();	
	 cout<<"ok="<<ok<<endl;

}

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------

And here's the output of the above code:

("QMYSQL3", "QMYSQL", "QODBC3", "QODBC", "QSQLITE")
QSqlError(-1, "Driver not loaded", "Driver not loaded")
ok=0
Press any key to continue . . .

Can you please guide me on resolving the issue here? What am I doing wrong here?

Thanks,
Ashish

[wysota]

QSqlDatabase::addDatabase() is a static method.

[MarkoSan]

I've downloaded Qt 4.5.1 Opensource, Installed it (with mingw) and built mysql plugin according to Qt Centre's Wiki. Then I ran my app and I also get "Driver not loaded". Can someone help me here since I do not know what to do anymore ....

[lyuts]

I have a similar problem. I have built the PSQL driver and now it is the system's search path. But my application doesn't find this driver.