Connect to MYSQL failed in Qt

SGaist · wrote on 7 May 2021, 10:59

The SQL module is supported in Qt 6. However the MySQL plugin might not be provided because Oracle changed their licensing.

As for your build issue: -L is for giving path to search, it's -l for stating the name of the library.

Christian Ehrlicher · 7 May 2021, 11:01

So the QtSql module has no errors - please stay specific!

else:unix: LIBS += -L$$PWD/lib/libmysql.lib

This is for sure not correct.

ELEMENTICY · 5 Jul 2021, 11:02

@Christian-Ehrlicher but qtsql mysql plugin doesnt provided as @SGaist said it,i tried add it by following youtube tutorial,it still doesnt.Lemme try it again and send the error here

ELEMENTICY · 7 May 2021, 11:03

@Christian-Ehrlicher

This is for sure not correct.

oh,how do i fix it?

SGaist · 7 May 2021, 11:05

@ELEMENTICY said in Connect to MYSQL failed in Qt:

@Christian-Ehrlicher

This is for sure not correct.

oh,how do i fix it?

Re-read my previous answer.

ELEMENTICY · S SGaist 7 May 2021, 11:03

@SGaist so i have to make it

win32:CONFIG(release, debug|release): LIBS += -L$$PWD/lib/ -l libmysql
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/lib/ -l libmysqld
else:unix: LIBS += -L$$PWD/lib/ -l libmysql

?

SGaist · 7 May 2021, 11:12

No space no "lib" prefix.

It's explained in the documentation

ELEMENTICY · 7 May 2021, 11:14

@SGaist my current profile code:

win32:CONFIG(release, debug|release): LIBS += -L$$PWD/lib/ -llibmysql
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/lib/ -llibmysqld
else:unix: LIBS += -L$$PWD/lib/ -llibmysql

documentation:

LIBS += -L"3rdparty/CatWhisperer/lib" -lCatWhisperer

i got this error:
:-1: error: error: cannot find -llibmysql

proof that path exists:

Christian Ehrlicher · wrote on 7 May 2021, 11:13

@ELEMENTICY said in Connect to MYSQL failed in Qt:

And yea,use qt sql it just give like 11 error

What does this mean?

SGaist · 7 May 2021, 11:16

@ELEMENTICY did you read what I wrote ? No "lib" prefix.

ELEMENTICY · 7 May 2021, 18:43

@SGaist
current code:

win32:CONFIG(release, debug|release): LIBS += -L$$PWD/lib/libmysql
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/lib/libmysqld
else:unix: LIBS += -L$$PWD/lib/libmysql

idk if i misunderstanded what u mean,but it still give error ;/
or u mean i have to remove that -L

ELEMENTICY · 7 May 2021, 18:44

@SGaist and yea i dont know if its because im working on a android app,so it doesnt work

SGaist · wrote on 7 May 2021, 18:43

@ELEMENTICY said in Connect to MYSQL failed in Qt:

@SGaist
current code:
win32:CONFIG(release, debug|release): LIBS += -L$$PWD/lib/libmysql
else:win32:CONFIG(debug, debug|release): LIBS += -L$$PWD/lib/libmysqld
else:unix: LIBS += -L$$PWD/lib/libmysql
idk if i misunderstanded what u mean,but it still give error ;/
or u mean i have to remove that -L

You have to understand what -L and -l each do. I have already explained that before. So please re-read the corresponding answers.

SGaist · wrote on 7 May 2021, 18:44

@ELEMENTICY said in Connect to MYSQL failed in Qt:

@SGaist and yea i dont know if its because im working on a android app,so it doesnt work

Oracle does not provide pre-built binaries for Android.

ELEMENTICY · 5 Aug 2021, 05:08

@SGaist dude,im so tired...
Can you pleaseee write the 3 lines of code for me?
Please... i hope after you see this message,you wont just ignore and think i never hard work on it..But im tired for just add a simple library already...
It will be the BEST help for me

My current code...

win32:CONFIG(release, debug|release): LIBS += $$PWD/lib/ -llibmysql
else:win32:CONFIG(debug, debug|release): LIBS += $$PWD/lib/ -llibmysqld
else:unix: LIBS += $$PWD/lib/ -llibmysql

Error:
:-1: error: error: cannot open C:/Users/ELEMENT/Documents/PosSystem/Pos/lib/: Permission denied
I opened QT Creator with Administrator,still same...

I also tried..

win32:CONFIG(release, debug|release): LIBS += $$PWD/lib/libmysql
else:win32:CONFIG(debug, debug|release): LIBS += $$PWD/lib/libmysqld
else:unix: LIBS += $$PWD/lib/libmysql

Error:
:-1: error: no such file or directory: 'C:/Users/ELEMENT/Documents/PosSystem/Pos/lib/libmysql' clang++: error: no such file or directory: 'C:/Users/ELEMENT/Documents/PosSystem/Pos/lib/libmysql' make: *** [Makefile:79: libPos_x86_64.so] Error 1
Seems like that one is the wrong way to do without adding -l

appreciate it...

ELEMENTICY · wrote on 8 May 2021, 05:18

@SGaist I removed:

win32:CONFIG(release, debug|release): LIBS += $$PWD/lib/ -llibmysql
else:win32:CONFIG(debug, debug|release): LIBS += $$PWD/lib/ -llibmysqld
else:unix: LIBS += $$PWD/lib/ -llibmysql

And tried only

LIBS += -L"lib" -llibmysql

Still error:
:-1: error: error: cannot find -llibmysql

SGaist · 8 May 2021, 10:14

"Drop the lib prefix": -lmysql

To repeat myself: Oracle does not provide pre-built binaries for Android.

Also, @Christian-Ehrlicher already asked you several times: what exact error did you get with the QtSql module ?

ELEMENTICY · 5 Aug 2021, 10:15

@SGaist ok its weird,it now dont give any error.But its EXCELENT!
But it unable to connect to Server
My code:

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
        db.setHostName("localhost");
        db.setDatabaseName("pos");
        db.setUserName("root");

        if (!db.open()){
            ui->error->setText("Oops,Unable to connect to Server!Please contact your Administrator for help.");
        }

Includes:

#include <QtSql/QSql>
#include <QtSql/QSqlDatabase>
#include <QtSql/QSqlDriver>
#include <QtSql/QSqlQuery>

and i also added sql to Qt in Profile

QT       += core gui sql

ELEMENTICY · 8 May 2021, 10:59

@ELEMENTICY im sure i entered correct server info

JonB · 5 Aug 2021, 10:59

@ELEMENTICY
So your root user has no password to connect to MySQL?

If db.open() fails, why don't you print out db.lastError() into your error message?