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Forum Update on Monday, May 27th 2025

Selecting data from mysql using qt?

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  • D Offline
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    Dii
    wrote on 12 Oct 2010, 09:49 last edited by
    #63

    nope, you had ` before the root and not '
    that was the error

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    • D Offline
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      Dii
      wrote on 12 Oct 2010, 09:51 last edited by
      #64

      ok, wait a second, I checked it in the meantime and it won't work without password, stay tuned, I post the right command

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      • D Offline
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        doforumda
        wrote on 12 Oct 2010, 09:51 last edited by
        #65

        you mean like this
        grant all on testTwo.* to root@localhost ;
        if yes it also displaying same error

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        • D Offline
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          Dii
          wrote on 12 Oct 2010, 09:52 last edited by
          #66

          so, here we go:

          grant all on testTwo.* to 'root'@'localhost' identified by 'password';

          Make the right apostrophes! :) You have to set the password in your Qt app too.

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          • D Offline
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            Dii
            wrote on 12 Oct 2010, 09:52 last edited by
            #67

            ok, wait I see

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            • D Offline
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              Dii
              wrote on 12 Oct 2010, 09:53 last edited by
              #68

              the Devnet's forum motor changes the apostrophes somehow... use the straight apostrophes everywhere
              I mean this @'@

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              • D Offline
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                doforumda
                wrote on 12 Oct 2010, 10:01 last edited by
                #69

                mysql query did its job its now successful but when i use qt code and try to make it run it displays same error

                @
                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
                @

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                • D Offline
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                  doforumda
                  wrote on 12 Oct 2010, 10:02 last edited by
                  #70

                  wait i think the query is not sucessful because it displays this message 0 rows affected
                  @
                  mysql> grant all on testTwo.* to 'root'at'localhost' identified by 'password';
                  Query OK, 0 rows affected (0.01 sec)
                  @

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                  • L Offline
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                    lyuts
                    wrote on 12 Oct 2010, 10:03 last edited by
                    #71

                    Add this to your code after connecting:

                    @qDebug() << db.lastError().text();@

                    And tell us what the error is.

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

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                    • L Offline
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                      lyuts
                      wrote on 12 Oct 2010, 10:04 last edited by
                      #72

                      [quote author="doforumda" date="1286877766"]wait i think the query is not sucessful because it displays this message 0 rows affected
                      @
                      mysql> grant all on testTwo.* to 'root'at'localhost' identified by 'password';
                      Query OK, 0 rows affected (0.01 sec)
                      @[/quote]

                      Did you run that command with 'password' instead of '123456'?

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

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                      • D Offline
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                        Dii
                        wrote on 12 Oct 2010, 10:05 last edited by
                        #73

                        0 rows is just fine with the grant command... have you set the password on

                        @db.setPassword("password");@

                        ?

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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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                          • L Offline
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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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                            • D Offline
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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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                              • 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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                                          doforumda
                                          wrote on 12 Oct 2010, 10:43 last edited by
                                          #82

                                          same error again

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                                          12 Oct 2010, 10:04

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