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    Call for Presentations - Qt World Summit

    Selecting data from mysql using qt?

    General and Desktop
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    • D
      doforumda last edited by

      this is the output after adding lastError.text()
      @
      Starting /home/zafar/c++/dbExample-build-desktop/dbExample...
      " "
      false
      QSqlQuery::exec: database not open
      /home/zafar/c++/dbExample-build-desktop/dbExample exited with code 0
      @

      lyut: yes i use command with 'password' not '123456'

      Dii sorry i didnt understand this db.setPassword("password");
      where should i set this

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      • L
        lyuts last edited by

        [quote author="doforumda" date="1286878193"]
        lyut: yes i use command with 'password' not '123456'

        Dii sorry i didnt understand this db.setPassword("password");
        where should i set this[/quote]

        1. I assume you should have specified the actual password when running that query.
        2. @db.setPassword("password");@ should be added to your source code just where you set db options.

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

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        • D
          doforumda last edited by

          i ran query again with actual password
          i have already setup password in my qt code here it is
          @
          #include <QApplication>
          #include <QtSql>

          int main(int argc, char *argv[])
          {
          QCoreApplication a(argc, argv);

          QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
          db.setDatabaseName("testTwo");
          db.setUserName("root");
          db.setPassword("123456");
          db.setHostName("localhost");
          
          qDebug() << db.lastError().text();
          
          bool ok = db.open();
          qDebug() << ok;
          
          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 0;
          

          }

          @

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          • D
            Dii last edited by

            db.lasterror().text() should come after line 16 (db.open()).
            The password in the Qt code must be the same what you have specified in the GRANT command above.

            I suspect probably, you haven't made the database and the table in mysql yet, if you go back to mysql command line, what do you get by these commands:

            @SHOW databases;

            USE testTwo;

            SHOW tables;@

            I go to dinner, be back in a few minutes :)

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            • L
              lyuts last edited by

              You put my debug before opening the connection. Put it after.

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

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              • D
                doforumda last edited by

                i changed db.lastError().text(); and place it after db.open()
                this is the output
                @
                Starting /home/zafar/c++/dbExample-build-desktop/dbExample...
                "Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) QMYSQL: Unable to connect"
                false
                QSqlQuery::exec: database not open
                /home/zafar/c++/dbExample-build-desktop/dbExample exited with code 0
                @

                the commands in mysql displayed are here
                repectively to your commands

                @
                mysql> show databases;
                +--------------------+
                | Database |
                +--------------------+
                | information_schema |
                | cdcol |
                | mysql |
                | phpmyadmin |
                | test |
                | testTwo |
                +--------------------+
                6 rows in set (0.01 sec)

                mysql> use testTwo
                Database changed
                mysql> show tables
                -> ;
                +-------------------+
                | Tables_in_testTwo |
                +-------------------+
                | testTable |
                +-------------------+
                1 row in set (0.01 sec)

                @

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                • D
                  doforumda last edited by

                  any clues?

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                  • L
                    lyuts last edited by

                    Change the 19th line to

                    @QSqlQuery query(db);@

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

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                    • D
                      doforumda last edited by

                      same error again

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                      • L
                        lyuts last edited by

                        Take a look into mysql logs to see what happens when you are trying to connect from your application.

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

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                        • D
                          doforumda last edited by

                          how can i check that mysql logs and from where?

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                          • L
                            lyuts last edited by

                            [quote author="doforumda" date="1286880547"]how can i check that mysql logs and from where? [/quote]

                            Try to find them:
                            @find /opt/lampp -name log -type d@

                            When you find the log directory, find a log for mysql and use tail utility:

                            @tail -f /path/to/mysql.log@

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

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                            • D
                              doforumda last edited by

                              this command didnt return something
                              @
                              root@zafar-laptop:/# find /opt/lampp -name log -type d
                              root@zafar-laptop:/#
                              @

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                              • D
                                doforumda last edited by

                                i have a folder inside lampp with the name logs. is it the one which your are talking about

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                                • L
                                  lyuts last edited by

                                  Solution 1:
                                  @find /opt/lampp -name '*.log'@
                                  This might need sudo'ing.

                                  Solution 2:
                                  If 1st fails then you need to find the config files for mysql (it should be located in /opt/lampp directory) and try to find out what is the location of mysql's log files.

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

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                                  • D
                                    doforumda last edited by

                                    there are 6 files in there but no mysql.log

                                    these are the files
                                    access_log, cgisock.1693, error_log, httpd.pid, php_error_log, ssl_request_log

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                                    • D
                                      Dii last edited by

                                      Don't bother with the log files, I guess Qt looks at the wrong place for the socket file...

                                      Let's check this line in your mysql config file (my.cnf):

                                      socket = /var/run/mysqld/mysqld.sock

                                      You should find my.cnf in /etc/ or /etc/mysql/ ... I don't know ubuntu that much.

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                                      • D
                                        doforumda last edited by

                                        1st solution returns this
                                        @
                                        root@zafar-laptop:/# find /opt/lampp -name *.log
                                        /opt/lampp/htdocs/xampp/contrib/sqlnet.log
                                        @

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                                        • D
                                          doforumda last edited by

                                          with which editor i can view that .conf file. with gedit or something.

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                                            lyuts last edited by

                                            [quote author="¤ Dii ¤" date="1286881470"]
                                            You should find my.cnf in /etc/ or /etc/mysql/ ... I don't know ubuntu that much.[/quote]

                                            I don't think that this config will be in /etc. He uses lampp - a preconfigured bundle. That config might be in /opt/lampp.

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

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