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Selecting data from mysql using qt?

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    Guest
    wrote on last edited by
    #2

    Line no. 22 and 23, can just be replaced with ...

    @
    QSqlQuery query("SELECT * FROM testTable");
    @

    But also, do check the documentation for QSqlQuery, where it is recomended NOT to use SELECT *

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      doforumda
      wrote on last edited by
      #3

      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

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        tony
        wrote on last edited by
        #4

        Maybe an "#include <QVariant>" is missing at the top?

        T.

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          MTK358
          wrote on last edited by
          #5

          Why not just

          @#include <QtCore>
          #include <QtSql>@

          and not worry about every single class you use?

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            tony
            wrote on last edited by
            #6

            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.

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              doforumda
              wrote on last edited by
              #7

              i add #include <QVariant>

              now it is saying
              @
              QSqlQuery::exec: database not open
              @

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                Dmytro
                wrote on last edited by
                #8

                Try to use QSqlQuery::lastError() for find problem

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                  doforumda
                  wrote on last edited by
                  #9

                  what is the problem now in my code why it is not opening database?

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                    tony
                    wrote on last edited by
                    #10

                    Did you leave

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

                    commented?

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                      doforumda
                      wrote on last edited by
                      #11

                      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

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                        doforumda
                        wrote on last edited by
                        #12

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

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

                        commented?[/quote]

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                          Dmytro
                          wrote on last edited by
                          #13

                          Try uncomment line 23

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                            doforumda
                            wrote on last edited by
                            #14

                            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

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                              Dmytro
                              wrote on last edited by
                              #15

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

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

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                                doforumda
                                wrote on last edited by
                                #16

                                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?

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                                  doforumda
                                  wrote on last edited by
                                  #17

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

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                                    Dmytro
                                    wrote on last edited by
                                    #18

                                    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

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                                      doforumda
                                      wrote on last edited by
                                      #19

                                      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

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                                        Dmytro
                                        wrote on last edited by
                                        #20

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

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                                          doforumda
                                          wrote on last edited by
                                          #21

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

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