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Selecting data from mysql using qt?

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  • D Offline
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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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    • L Offline
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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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      • D Offline
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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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            • D Offline
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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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                  • L Offline
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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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                      • D Offline
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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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                        • L Offline
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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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                            • D Offline
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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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                              • D Offline
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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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                                • D Offline
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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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                                  • L Offline
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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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                                      Dii
                                      wrote on 12 Oct 2010, 11:08 last edited by
                                      #94

                                      BTW a quick sum:

                                      • mysql is installed
                                      • database and tables are created
                                      • access is granted
                                      • qt code looks fine

                                      I see two possibilities here: libmysqlclient is missing, or the socket file is at different place.

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                                        doforumda
                                        wrote on 12 Oct 2010, 11:09 last edited by
                                        #95

                                        the file my.cnf is in etc/mysql folder

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                                          Dii
                                          wrote on 12 Oct 2010, 11:10 last edited by
                                          #96

                                          doforumda: use gedit

                                          sudo gedit /etc/mysql/my.cnf

                                          at least most of the ubuntu machines have the config file there.

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                                          12 Oct 2010, 10:56

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