Here is the first edition and after the translation in English because I am a new member and this is my first thread. I don’t know that I must only write with the English an offer my excuses for that error and excuse me for my bad English.
= = = = = = Begin of the first edition = = = = = =
Xubuntu Ubuntu 18.04.3 LTS
QT 5.12.3
MySQLClient : libmysqlclient.so.20.3.14
m_QSQLDB_r_MaGestionTest->addDatabase("QMYSQL3", "MaSGBDR");
erreur provoquant l'arrêt du module avec le message :
QSqlDatabase: QMYSQL3 driver not loaded QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QODBC QODBC3 QPSQL QPSQL7
Il semblerait que le load du driver ne puisse se faire. Faut-il adapter un PATH pour XUBUNTU ou pour QT ou QMAKE ?
Par avance merci pour une réponse.
= = = = = = End of the first edition = = = = = =
Now is my translation
My Operating System is Xubuntu Ubuntu 18.04.3 LTS
My IDE is QT 5.12.3
MySQLClient for Qt is libmysqlclient.so.20.3.14
The problem become when I use this instruction*:
m_QSQLDB_r_MaGestionTest->addDatabase("QMYSQL3", "MaSGBDR");
m_QSQLDB_r_MaGestionTest is defined in MainWindow.h by
#include <QtSql/QSqlDatabase>
QSqlDatabase *m_QSQLDB_r_MaGestionTest; // OBjet pour accéder à la base MySQL
The error is*:
QSqlDatabase: QMYSQL3 driver not loaded QSqlDatabase: available drivers: QSQLITE
MYSQL QMYSQL3 QODBC QODBC3 QPSQL QPSQL7

The program was ending abruptly.
The driver can’t loaded. What do I have to change PATH in XUBUNTU, Qt or QMAKE?
Thanks in advance!

Try to ask your question in English. This forum is English only - not in order to exclude you, but to include everybody else.

You say that when adding a database in a piece of software named QSqlDatabase, you get the message QMYSQL3 driver not loaded and wonder what you need to do to load this driver.

When you enter the error message into a search engine, you get many results. Here is the same problem with the QMYSQL driver: https://stackoverflow.com/questions/...ver-not-loaded. And here specifically for Ubuntu: https://stackoverflow.com/questions/...u-15-04-64bits.

Hi berndbausch,
Thank for your fast response. I am a new member to Lq. I have subsribing yesterday before my post.
I was so tired yesterday night to write in English. I write and talk so bad in English. Excuse me for the faults.
I am 66 years old and ha stop to work from 4 years. My culture in langage and system was learning during the 1970 years. The system was IBM 370 MVS and VM, GCOS for machines Bull an Mitra 125. The langage was Fortran, COBOL, PL-1, assembly 370 and assembly Mitra 125.
Now I want developping for me application on PC. So, I have XUBUNTU 18,04 LTS on my phisical computer with VirtualBox to create many computers. I have a old XP-SP3, a XUBUNTU for servers DNS, APACHE2, MySQL Server, Adminer and a XUBUNTU Desktop for developpement with QT and C++, client MySQL, DJANGO with Python and Pip. So I am a beginner to UBUNTU, C++ with Object Programming, Python, Php, MySQL and the SGBDR technology.
Now XUBUNTU for the Host and the Vms are operational, MySQL Server with command lines is OK and verify with Adminer. My first tests with QT are operational. I can show cascading windows, write events in my logs.

The new operation is the use of MySQL base from a Qt application.
2 Days ago, I am searching a solution to my problem about the driver MySQL for Qt.
In /usr/lib/x86_64-linux-gnu, is libmysqlclient.so.20.3.14.
I had shown in many pages web from stackoverflow that I must create links for libmysqlclient.so.18 to libmysqlclient.so.20 and I have create an other for libmysqlclient.so.20 to libmysqlclient.so.20.3.14 and also others with -r for libmysqlclient_r.a, libmysqlclient_r.so, libmysqlclient_r.so.20 and libmysqlclient_r.so.20.3.14 to libmysqlclient.a, libmysqlclient.so, libmysqlclient.so.20 and libmysqlclient.so.20.3.14.
I have modify my etc/environnement with*:
PATH="/home/UserData/MesScripts/Bash/DJANGO:/home/UserData/MesScripts/Bash/:/home/UserData/MesApplis/MesApplisDjango/PCH240Env3.7MySql/bin/:/home/UserData/MesApplis/MesApplisDjango/PCH240Env3.7MySql/lib/:/usr/bin/python3.7:/usr/lib/x86_64-linux-gnu:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:"
QTDIR=/home/paul-au-chon/Qt5.12.3/5.12.3/gcc_64
I have also modify my ~/,bashrc to include*:
export PATH="/home/UserData/MesScripts/Bash/DJANGO:/home/UserData/MesScripts/Bash/:/home/UserData/MesApplis/MesApplisDjango/PCH240Env3.7MySql/bin/:/home/UserData/MesApplis/MesApplisDjango/PCH240Env3.7MySql/lib/:/usr/bin/python3.7:/usr/lib/x86_64-linux-gnu:/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin:"

I have also the error. I don’t understand what is the object for the driver searching by Qt, who is there and who Qt find it.

One more time, thanks for your response and, perheaps, could you more help me. I must learning many news to create my project.