QT client development -- driver loading problem of connecting to MySQL database

Preface

• For rigid contact Qt For the developers , Connecting to a database is a headache , I have just come into contact with Qt I also encountered many pits , In connection mysql It took two or three days to solve the database problem , This document records the solution to Qt Connect mysql It's a driving problem , Hope to help more developers avoid detours ！
• If it helps you , You might as well click three times ！
• This article is the experience summary of bloggers ！ Some operations refer to the articles of other bloggers , But because of the long time , Original link not saved , If you have any questions, I attach a reference link ！

resolvent 1： Use mysql The compiled driver in the installation directory 【 Not necessarily effective 】

because mysql Drive for all Qt Versions are universal , therefore , This method may not be effective . It's been tested before ,Qt5.9 MSVC2017 and mysql5.7 It works , Others are invalid

• Method ： take mysql Of lib Copy the dynamic library in the folder to Qt Corresponding to the compiler bin Under the directory

QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QODBC QODBC3 QPSQL QPSQL7
error open database "Driver not loaded Driver not loaded"

resolvent 2： Manually compile mysql【 Match the compiler used 】

• Method ：

  • ① Get into Qt Source directory 【 install Qt You need to choose installation source This directory is available only 】：D:\DevEnv\Qt\5.15.2\Src\qtbase\src\plugins\sqldrivers\mysql

  • ② modify mysql.pro file

    #  Add the following information , And comment out QMAKE_USE += mysql
    INCLUDEPATH +="D:\DevEnv\mysql-8.0.23-winx64\include"  # mysql Header Directory 
    LIBS +="D:\DevEnv\mysql-8.0.23-winx64\lib\libmysql.lib"  # mysql Library file directory 
    DESTDIR  = ../mysql/lib/  #  Specify the output location after compilation 
    

    

  • ③ compile
    

      >  Use Qt 5.15.2 MinGW 64bit compile , The generated dynamic library is only suitable for this compiler 
    

  • There's a problem 【 It seems that this problem can be ignored 】
    

    • terms of settlement , Modify the following documents ：
      

• compile MSVC There may be ：Qt And msvc-version.conf loaded but QMAKE_MSC_VER isn’t set

  terms of settlement ： stay D:\DevEnv\Qt\5.15.2\msvc2019_64\mkspecs\common Of msvc-version.conf Add... To the configuration file QMAKE_MSC_VER = 1900 that will do
  

  • Compile again , Generate lib Folder 【MinGW and MSVC The generated files are different 】

  

  • Copy lib Folder files to

    

    Be careful ： This method also needs to copy mysql/lib Files in directory to Qt Of bin Under the table of contents

• Connect the test

  qDebug() << QSqlDatabase::drivers();
  QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
  db.setHostName("localhost");
  db.setDatabaseName("wordmemory");
  db.setUserName("root");
  db.setPassword("123456");
  bool ok = db.open();
  
  if (ok) qDebug() << " Connect to database ok";
  else qDebug() << " Failed to connect to database ";