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Selecting data from mysql using qt?

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  • D Offline
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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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    • D Offline
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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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                          doforumda
                          wrote on last edited by
                          #22

                          anyone who can help?

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                            Dmytro
                            wrote on last edited by
                            #23

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

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                              doforumda
                              wrote on last edited by
                              #24

                              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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                                Dii
                                wrote on last edited by
                                #25

                                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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                                  doforumda
                                  wrote on last edited by
                                  #26

                                  i now put password for root at localhost.
                                  when i place qDebug() << ok then it displays this
                                  @
                                  false
                                  QSqlQuery::exec: database not open
                                  @

                                  false might be the value of ok.

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                                    lyuts
                                    wrote on last edited by
                                    #27

                                    Are you able to connect to your DB from shell?

                                    I'm a rebel in the S.D.G.

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                                      doforumda
                                      wrote on last edited by
                                      #28

                                      i dont know how to connect to my DB from shell. I install xampp which is easy for me to manage my databases.
                                      how can i connect from shell?

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                                        lyuts
                                        wrote on last edited by
                                        #29

                                        @mysql -h host -D dbname -u user@

                                        I guess your can omit host parameter if you are connecting to localhost. You might need to specify "-p password" switch also (depends on mysql configuration).

                                        I'm a rebel in the S.D.G.

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                                          doforumda
                                          wrote on last edited by
                                          #30

                                          i think i did not install any mysql client. bcause it displays this output
                                          @
                                          root@zafar-laptop:/# mysql -h localhost -D testTwo -u root -p xxxxxx
                                          The program 'mysql' can be found in the following packages:

                                          • mysql-client-core-5.1
                                          • mysql-client-5.0
                                          • mysql-cluster-client-5.1
                                            Try: apt-get install <selected package>
                                            @
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