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    Selecting data from mysql using qt?

    General and Desktop
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    • T
      tony last edited by

      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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      • D
        doforumda last edited by

        i add #include <QVariant>

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

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        • D
          Dmytro last edited by

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

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          • D
            doforumda last edited by

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

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            • T
              tony last edited by

              Did you leave

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

              commented?

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              • D
                doforumda last edited by

                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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                • D
                  doforumda last edited by

                  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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                  • D
                    Dmytro last edited by

                    Try uncomment line 23

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                    • D
                      doforumda last edited by

                      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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                      • D
                        Dmytro last edited by

                        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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                        • D
                          doforumda last edited by

                          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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                          • D
                            doforumda last edited by

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

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                            • D
                              Dmytro last edited by

                              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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                              • D
                                doforumda last edited by

                                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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                                • D
                                  Dmytro last edited by

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

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                                  • D
                                    doforumda last edited by

                                    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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                                    • D
                                      doforumda last edited by

                                      anyone who can help?

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                                      • D
                                        Dmytro last edited by

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

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                                        • D
                                          doforumda last edited by

                                          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

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                                          • D
                                            Dii last edited by

                                            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.)

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