I can't connect to my local database.

leonidas_lolo

[ SOLVED ]

Hello,
I want to connect to my local database from QT but when I run my project it gives me this error from db.lasterror().texet() :
QSqlDatabase: QMYSQL driver not loaded
QSqlDatabase: available drivers: QSQLITE QMYSQL QMYSQL3 QPSQL QPSQL7

My OS is Centos 7 64 Bit.
Please help.

hpollak

@leonidas_lolo said:

QSqlDatabase: QMYSQL driver not loaded

Take a look on this thread:
QSqlDatabase: QMYSQL driver not loaded but available

leonidas_lolo

I did what the thread said but it didn't worked. my code is :
main.cpp file

#include <QCoreApplication>
#include <QtSql>
#include <QDebug>

int main(int argc, char *argv[])
{
    QCoreApplication a(argc, argv);
    QSqlDatabase db;
    db = QSqlDatabase::addDatabase("QMYSQL");
    db.setHostName("localhost");
    db.setPort(3306);
    db.setUserName("thename");
    db.setPassword("thepassword");
    db.setDatabaseName("thedatabase");
    qDebug()<<db.open();
    return a.exec();
}

my .pro file have the followings :

QT       += core
QT       += sql
QT       -= gui
TARGET = DB_Programming
CONFIG   += console
CONFIG   -= app_bundle
TEMPLATE = app
SOURCES += main.cpp

Please advise.

Edited: Put code after ``` (3 backticks) and close with the same - p3c0

simow

@leonidas_lolo Hi, normally everything should be working out of the box after installing Qt and the MySQL database.
Just to double-check:

you added a line like qDebug() << "Plugins loaded from: " << QCoreApplication::libraryPaths(); to make sure the plugins path with the sqldrivers subdirectory is in there (it should, otherwise you won't get the list containing QMYSQL in "available drivers")
you ran ldd /usr/lib/qt/plugins/sqldrivers/libqsqlmysql.so to check if there is an entry like libmysqlclient.so.18 => /usr/lib/libmysqlclient.so.18 (0xb738d000)

One other thing that just came to my mind: You don't have multiple versions of MySQL installed or the like (e.g. MySQL and MariaDB)?

TheBadger

I do not have experiance with MySQL but with PostrgeSQL the problem (every time) was that the PostgreSQL libs were not available to the application. We had to either copy the dlls into the same folder as the application or make it avaiable in the PATH (windows)

So on Linux make sure that the libs are located in the LD_LIBRARY_PATH

leonidas_lolo

I added the line to my .cpp file
qDebug() << "Plugins loaded from: " << QCoreApplication::libraryPaths(); and it says :
("/opt/Qt/5.4/gcc_64/plugins", "/home/<username>/Documents/Qt Projects/<another folder>/build-DB_Programming-Desktop_Qt_5_4_0_GCC_64bit-Release")
I searched in that directory and I do have the folder sqldrivers.
I don't have any file libqsqlmysql.so on the /usr/lib/qt4/plugins/sqldrivers.
The only file i have is libqsqlite.so.

The file libqsqlmysql.so is locate at my installation directory /opt/Qt/5.4/gcc_64/plugins/sqldrivers.
I make a copy and paste it to the previous direcotry but did not wokr either.

When I ran the ldd on libqsqlmysql.so on the /opt/Qt/5.4/gcc_64/plugins/sqldrivers location it says:
linux-vdso.so.1 => (0x00007fffdfd11000)
libmysqlclient_r.so.16 => not found
libQt5Sql.so.5 => /opt/Qt/5.4/gcc_64/plugins/sqldrivers/../../lib/libQt5Sql.so.5 (0x00007f4f00daf000)
libQt5Core.so.5 => /opt/Qt/5.4/gcc_64/plugins/sqldrivers/../../lib/libQt5Core.so.5 (0x00007f4f00673000)
libstdc++.so.6 => /lib64/libstdc++.so.6 (0x00007f4f0036c000)
libc.so.6 => /lib64/libc.so.6 (0x00007f4efffaa000)
libpthread.so.0 => /lib64/libpthread.so.0 (0x00007f4effd8e000)
libicui18n.so.53 => /opt/Qt/5.4/gcc_64/plugins/sqldrivers/../../lib/libicui18n.so.53 (0x00007f4eff942000)
libicuuc.so.53 => /opt/Qt/5.4/gcc_64/plugins/sqldrivers/../../lib/libicuuc.so.53 (0x00007f4eff5b6000)
libdl.so.2 => /lib64/libdl.so.2 (0x00007f4eff3b2000)
libgthread-2.0.so.0 => /lib64/libgthread-2.0.so.0 (0x00007f4eff1b0000)
librt.so.1 => /lib64/librt.so.1 (0x00007f4efefa7000)
libglib-2.0.so.0 => /lib64/libglib-2.0.so.0 (0x00007f4efec7e000)
libm.so.6 => /lib64/libm.so.6 (0x00007f4efe97c000)
libgcc_s.so.1 => /lib64/libgcc_s.so.1 (0x00007f4efe765000)
/lib64/ld-linux-x86-64.so.2 (0x00007f4f0121d000)
libicudata.so.53 => /opt/Qt/5.4/gcc_64/plugins/sqldrivers/../../lib/libicudata.so.53 (0x00007f4efd0dd000)

p3c0

@leonidas_lolo

libmysqlclient_r.so.16 => not found

install mysqlclient libraries.

leonidas_lolo

I run the command locate mysqlclient and I have the libraries.

[username@localhost ~]$ locate mysqlclient
/usr/lib64/libmysqlclient.so
/usr/lib64/libmysqlclient.so.18
/usr/lib64/libmysqlclient.so.18.1.0
/usr/lib64/libmysqlclient_r.so
/usr/lib64/libmysqlclient_r.so.18
/usr/lib64/libmysqlclient_r.so.18.1.0
/usr/lib64/mysql/libmysqlclient.so
/usr/lib64/mysql/libmysqlclient.so.18
/usr/lib64/mysql/libmysqlclient.so.18.0.0
/usr/lib64/mysql/libmysqlclient_r.so

p3c0

So I think the only way would be to try to link libmysqlclient_r.so.16 to /usr/lib64/libmysqlclient.so.18 Or install old version of mysql client libraries which will contain *.so.16

leonidas_lolo

I fixed the problem by re-installing the QT Creator.