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Selecting data from mysql using qt?

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  • D Offline
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    doforumda
    wrote on 12 Oct 2010, 10:09 last edited by
    #74

    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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      lyuts
      wrote on 12 Oct 2010, 10:13 last edited by
      #75

      [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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        doforumda
        wrote on 12 Oct 2010, 10:15 last edited by
        #76

        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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          Dii
          wrote on 12 Oct 2010, 10:18 last edited by
          #77

          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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            lyuts
            wrote on 12 Oct 2010, 10:21 last edited by
            #78

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

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

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              doforumda
              wrote on 12 Oct 2010, 10:24 last edited by
              #79

              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 Offline
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                doforumda
                wrote on 12 Oct 2010, 10:38 last edited by
                #80

                any clues?

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                • L Offline
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                  lyuts
                  wrote on 12 Oct 2010, 10:41 last edited by
                  #81

                  Change the 19th line to

                  @QSqlQuery query(db);@

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

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                    doforumda
                    wrote on 12 Oct 2010, 10:43 last edited by
                    #82

                    same error again

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                    • L Offline
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                      lyuts
                      wrote on 12 Oct 2010, 10:46 last edited by
                      #83

                      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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                        doforumda
                        wrote on 12 Oct 2010, 10:49 last edited by
                        #84

                        how can i check that mysql logs and from where?

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                          lyuts
                          wrote on 12 Oct 2010, 10:54 last edited by
                          #85

                          [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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                            doforumda
                            wrote on 12 Oct 2010, 10:56 last edited by
                            #86

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

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                              doforumda
                              wrote on 12 Oct 2010, 11:01 last edited by
                              #87

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

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                                lyuts
                                wrote on 12 Oct 2010, 11:01 last edited by
                                #88

                                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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                                  doforumda
                                  wrote on 12 Oct 2010, 11:03 last edited by
                                  #89

                                  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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                                    Dii
                                    wrote on 12 Oct 2010, 11:04 last edited by
                                    #90

                                    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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                                      doforumda
                                      wrote on 12 Oct 2010, 11:05 last edited by
                                      #91

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

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                                        doforumda
                                        wrote on 12 Oct 2010, 11:07 last edited by
                                        #92

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

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                                          lyuts
                                          wrote on 12 Oct 2010, 11:07 last edited by
                                          #93

                                          [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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                                          12 Oct 2010, 10:46

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