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Cannot establish connection to MySQL database

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  • Cobra91151C Cobra91151

    Hello!

    I checked your code. The problem could be:

    1. If you are on Windows you must copy the libmysql.dll lib to the application directory.
    2. The database server is not started/working.

    Check it and it will work. Happy coding!

    H Offline
    H Offline
    Hmmm
    wrote on last edited by
    #5

    @Cobra91151 Thank you for your answer. I checked message log on MySQL, it says: 2019-06-30 16:15:59 - MySQL server is currently running
    Also I did copy libmysql.dll to the application directory but nothing helps :(

    Cobra91151C 1 Reply Last reply
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    • Christian EhrlicherC Offline
      Christian EhrlicherC Offline
      Christian Ehrlicher
      Lifetime Qt Champion
      wrote on last edited by
      #6

      Then please check with e.g. Dependency Walker if your qt mysql plugin really finds all necessary libraries.
      And where did you check for lastError?

      Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
      Visit the Qt Academy at https://academy.qt.io/catalog

      H 1 Reply Last reply
      1
      • H Hmmm

        @Cobra91151 Thank you for your answer. I checked message log on MySQL, it says: 2019-06-30 16:15:59 - MySQL server is currently running
        Also I did copy libmysql.dll to the application directory but nothing helps :(

        Cobra91151C Offline
        Cobra91151C Offline
        Cobra91151
        wrote on last edited by
        #7

        @Hmmm

        Ok. Try to navigate to the application directory and check if it contains: sqldrivers directory with qsqlmysql.dll lib?

        H 1 Reply Last reply
        1
        • Christian EhrlicherC Christian Ehrlicher

          Then please check with e.g. Dependency Walker if your qt mysql plugin really finds all necessary libraries.
          And where did you check for lastError?

          H Offline
          H Offline
          Hmmm
          wrote on last edited by
          #8

          @Christian-Ehrlicher I checked for lastError in the MainWindow, its not written above as I tried that later.
          About Dependeny Walker, I'm not very familiar with it, is this what I'm supposed to do:alt text

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          • Cobra91151C Cobra91151

            @Hmmm

            Ok. Try to navigate to the application directory and check if it contains: sqldrivers directory with qsqlmysql.dll lib?

            H Offline
            H Offline
            Hmmm
            wrote on last edited by
            #9

            @Cobra91151 This is what my application directory contains:
            0_1561906819643_969b9860-924a-4ccd-bd79-f1476b6ff7f6-image.png

            Cobra91151C 1 Reply Last reply
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            • H Hmmm

              @Cobra91151 This is what my application directory contains:
              0_1561906819643_969b9860-924a-4ccd-bd79-f1476b6ff7f6-image.png

              Cobra91151C Offline
              Cobra91151C Offline
              Cobra91151
              wrote on last edited by
              #10

              @Hmmm

              It is source directory. Application directory is where your .exe file is present (Debug/Release dir)! That's why it can't locate the MySQL libs. Copy libmysql.dll into Debug/Release dir (it depends on your Qt Creator configuration) and start the program. It 100% must work :)

              H 1 Reply Last reply
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              • Christian EhrlicherC Offline
                Christian EhrlicherC Offline
                Christian Ehrlicher
                Lifetime Qt Champion
                wrote on last edited by
                #11

                @Hmmm said in Cannot establish connection to MySQL database:

                I checked for lastError in the MainWindow, its not written above as I tried that later.

                You have to call it after db.open()
                And you should check the qt mysql plugin, not the mysql dll ... it's qsqlmysql.dll/qsqlmysqld.dll and the location is for sure not in your source tree...

                Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                Visit the Qt Academy at https://academy.qt.io/catalog

                H 1 Reply Last reply
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                • Christian EhrlicherC Christian Ehrlicher

                  @Hmmm said in Cannot establish connection to MySQL database:

                  I checked for lastError in the MainWindow, its not written above as I tried that later.

                  You have to call it after db.open()
                  And you should check the qt mysql plugin, not the mysql dll ... it's qsqlmysql.dll/qsqlmysqld.dll and the location is for sure not in your source tree...

                  H Offline
                  H Offline
                  Hmmm
                  wrote on last edited by
                  #12

                  @Christian-Ehrlicher Ok, about lastError, I put it after and it says:

                  QSqlError("2059", "QMYSQL: Unable to connect", "Authentication plugin 'caching_sha2_password' cannot be loaded: The specified module could not be found.\r\n")`
                  

                  And this is the ouput of qsqlmysql.dll in Dependeny Walker:

                  Error: At least one required implicit or forwarded dependency was not found.
                  Error: At least one module has an unresolved import due to a missing export function in an implicitly dependent module.
                  Error: Modules with different CPU types were found.
                  Error: A circular dependency was detected.
                  Warning: At least one delay-load dependency module was not found.
                  Warning: At least one module has an unresolved import due to a missing export function in a delay-load dependent module.
                  
                  1 Reply Last reply
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                  • Cobra91151C Cobra91151

                    @Hmmm

                    It is source directory. Application directory is where your .exe file is present (Debug/Release dir)! That's why it can't locate the MySQL libs. Copy libmysql.dll into Debug/Release dir (it depends on your Qt Creator configuration) and start the program. It 100% must work :)

                    H Offline
                    H Offline
                    Hmmm
                    wrote on last edited by
                    #13

                    @Cobra91151 Ok, my mistake. I did that now but still the same problem

                    1 Reply Last reply
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                    • Christian EhrlicherC Offline
                      Christian EhrlicherC Offline
                      Christian Ehrlicher
                      Lifetime Qt Champion
                      wrote on last edited by
                      #14

                      @Hmmm said in Cannot establish connection to MySQL database:

                      Authentication plugin 'caching_sha2_password' cannot be loaded: The specified module could not be found.

                      So this is a mysql problem, don't see what Qt can do against it. Maybe google can help here.

                      Qt Online Installer direct download: https://download.qt.io/official_releases/online_installers/
                      Visit the Qt Academy at https://academy.qt.io/catalog

                      1 Reply Last reply
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                      • H Offline
                        H Offline
                        Hmmm
                        wrote on last edited by
                        #15

                        Omg, I finally did it with running this SQL query:

                        ALTER USER 'yourusername'@'localhost' IDENTIFIED WITH mysql_native_password BY 'yourpassword';
                        

                        Thank you all for helping me :D

                        1 Reply Last reply
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