Build Mysql plugin for Qt

[faldzip]

can you check the returned value of query.exec() and try to read query results?

[Qt Coder]

query.exec();

is returning false

and when I fetch last error using

if(query.lastError().type() != QSqlError::NoError)
        {
            out << "\nError Occured 2  : " << query.lastError().text();
        }

if(query.lastError().type() != QSqlError::NoError)
        {
            out << "\nError Occured 2  : " << query.lastError().text();
        }

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the output is

Error Occured 2 : Driver not loaded Driver not loaded



what could be the possible error?

[Qt Coder]

again I followed following instructions

################################3
How to Build the Plug-in

1. Open a Qt Command Prompt and go to wherever you installed the MySQL server (C:\Program Files\MySQL\MySQL Server 5.0 is the default location).

2. Goto the sub-directory lib/opt and run reimp libmysql.lib to produce the liblibmysql.a file. This is the import library to use with MinGW.

3. Go to %QTDIR%/src/plugins/sqldrivers/mysql.

4. Run the following command: qmake -o Makefile "INCLUDEPATH+=C:\Progra~1\MySQL\MySQLS~1.0\include " "LIBS+=C:\Progra~1\MySQL\MySQLS~1.0\lib\opt\liblib mysql.a" mysql.pro (Notice that the Program Files directory name has been replaced by progra~1. This is because QMake cannot handle spaces in the search paths. Use dir /X <dirname> to find the shorter 8.3 version of the name.)

5. Run make - this should build the qsqlmysql.dll and libqsqlmysql.a files in the %QTDIR%/plugins/sqldrivers directory.

#########################

Till step 4 it runs successfully,but when I run make , after few hours of comiling it gives me error

"C:\MinGW\bin\..\lib\gcc\mingw32\3.4.2\..\..\..\.. \mingw32\bin\ld.exe: cannot fin
d -lmysql"


last I could make it successfulyy but the files produced were "libqsqlmysql4.a" and "qsqlmysql4.dll"

Now its showing me QMYSQL3 and QMYSQL in list of availabel drivers but as I execute or prepare for query it gives error "Driver not loaded"

[Qt Coder]

My problem is now,


Its showing me MYSQL,MYSQL3 in the list of availabel drivers also allows to connect to database,but as I prepare any query or execute it it gives error "Driver not loaded"





strange behaviour......

[faldzip]

can you show the whole code? because I can't find the place where you create the query object.

[Qt Coder]

QSqlQuery query;
 
   QFile file("d://DB_TRANS.txt");
    file.open(QIODevice::WriteOnly | QIODevice::Text);
    QTextStream out(&file);
 
   QStringList list = QSqlDatabase::drivers();
    QStringList::Iterator it = list.begin();
    while( it != list.end() ) {
        out << (*it) << "\n";
        ++it;
    }
 
     QSqlDatabase  db = QSqlDatabase::addDatabase("QMYSQL");
 
    db.setHostName("192.160.8.153");
    db.setDatabaseName("gaur01");
    db.setUserName("gaur");
    db.setPassword("gaur123");
    db.setPort(3306);
 
      if (!db.open()) {
         out <<"Error\n";
          out << db.lastError().driverText();
        out << "\n";
        out << db.lastError().databaseText();
    }
    else
    {
        out <<"DB open successfully";
        if(query.lastError().type() != QSqlError::NoError)
        {
 
            out << "\nError Occured 1 : " << query.lastError().text();
        }
 
     if(query.prepare("SELECT * FROM temp"))    
             out << "\nQuery prepared successfully : " ;
      else
      {
            out << "\nError in preparing query: "  << query.lastQuery();
            out << query.lastError().text();
      }
 
      if(query.exec())
      {
          out << "\nQuery executed successfully : " ;
            db.commit();
       }     
 
 
        if(query.lastError().type() != QSqlError::NoError)
        {
 
            out << "\nError Occured 2  : " << query.lastError().text();
        }

QSqlQuery query;
    
   QFile file("d://DB_TRANS.txt");
    file.open(QIODevice::WriteOnly | QIODevice::Text);
    QTextStream out(&file);

   QStringList list = QSqlDatabase::drivers();
    QStringList::Iterator it = list.begin();
    while( it != list.end() ) {
        out << (*it) << "\n";
        ++it;
    }

     QSqlDatabase  db = QSqlDatabase::addDatabase("QMYSQL");

    db.setHostName("192.160.8.153");
    db.setDatabaseName("gaur01");
    db.setUserName("gaur");
    db.setPassword("gaur123");
    db.setPort(3306);

      if (!db.open()) {
         out <<"Error\n";
          out << db.lastError().driverText();
        out << "\n";
        out << db.lastError().databaseText();
    }
    else
    {
        out <<"DB open successfully";
        if(query.lastError().type() != QSqlError::NoError)
        {

            out << "\nError Occured 1 : " << query.lastError().text();
        }

     if(query.prepare("SELECT * FROM temp"))    
             out << "\nQuery prepared successfully : " ;
      else
      {
            out << "\nError in preparing query: "  << query.lastQuery();
            out << query.lastError().text();
      }

      if(query.exec())
      {
          out << "\nQuery executed successfully : " ;
            db.commit();
       }     


        if(query.lastError().type() != QSqlError::NoError)
        {

            out << "\nError Occured 2  : " << query.lastError().text();
        }

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the output is

QMYSQL3
QMYSQL
QSQLITE
QODBC3
QODBC
 
DB open successfully
 
Error Occured 1 : Driver not loaded Driver not loaded
 
Error in preparing query: Driver not loaded Driver not loaded
 
Error Occured 2  : Driver not loaded Driver not loaded

QMYSQL3
QMYSQL
QSQLITE
QODBC3
QODBC

DB open successfully

Error Occured 1 : Driver not loaded Driver not loaded

Error in preparing query: Driver not loaded Driver not loaded

Error Occured 2  : Driver not loaded Driver not loaded

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[faldzip]

you are creating query (with a deafault database connection) before creating any databade connection. Try:

QSqlQuery query(db);

QSqlQuery query(db);

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after creating db.