Selecting data from mysql using qt?

doforumda · wrote on 12 Oct 2010, 11:59

lyut: sudo gedit /opt/lampp/etc/my.cnf this command does open my.cnf and it also have

socket = /opt/lampp/var/mysql/mysql.sock

in two lines means there are two entries for socket in my.cnf

lyuts · wrote on 12 Oct 2010, 12:10

I think this is rather rough solution, but worth trying:

@sudo mkdir -p /var/run/mysqld
sudo ln -s /opt/lampp/var/mysql/mysql.sock /var/run/mysqld/mysqld.sock@

doforumda · wrote on 12 Oct 2010, 12:10

so what next i think here the path for socket is correct because i have one mysql.sock file in that exactly same directory

doforumda · wrote on 12 Oct 2010, 12:13

you mean i should create a dir at opt/lampp/var/run/mysqld ????

doforumda · wrote on 12 Oct 2010, 12:20

millions of thanks to both of you TYUT and Dii. it works. one more question can please tell me what does this command do
@
sudo ln -s /opt/lampp/var/mysql/mysql.sock /var/run/mysqld/mysqld.sock
@

and also if i want to install everything from scratch then once i have to use this command to make it work?

Dii · wrote on 12 Oct 2010, 12:28

doforumda: the problem was ~small... the Qt mysql driver looks for the socket file (the connection to mysql) in the default location (var/run/mysqld/mysqld.sock), though you had it somewhere else, because your lampp package changed the path.

The "ln -s" made a symbolic link to that, so the /var/run/mysqld/mysqld.sock point to the /opt/lampp/var/mysql/mysql.sock. This way Qt can find it. If you do a new installation, with lampp, you should do it again, if you use the regular mysql package, probably, you won't face this problem.

lyuts: great work, we deserve these points :)

lyuts · wrote on 12 Oct 2010, 12:33

I think our solution is rough enough, but at least it works. I think the best solution is to set the socket parameter in my.cnf to /var/run/mysqld/mysqld.sock. But it is up to you doforumda.

bq. millions of thanks to both of you TYUT and Dii.

Hey, I'm lyuts, not TYUT :)

doforumda and ¤ Dii ¤, my congratulations, we did it.

Dii · wrote on 12 Oct 2010, 12:45

lyuts: I think that's the best solution, if he is changing the socket parameter of mysql probably he will screw up some other components in his LAMPP configuration. I don't recommend that.

lyuts · wrote on 12 Oct 2010, 13:34

I don't know what's going on within LAMPP and you might be right. It's just creating this symlink looks more like a workaround.

doforumda · wrote on 12 Oct 2010, 14:48

[quote author="lyuts" date="1286886793"]I think our solution is rough enough, but at least it works. I think the best solution is to set the socket parameter in my.cnf to /var/run/mysqld/mysqld.sock. But it is up to you doforumda.

bq. millions of thanks to both of you TYUT and Dii.

Hey, I'm lyuts, not TYUT :)

doforumda and ¤ Dii ¤, my congratulations, we did it.[/quote]

sorry I wrote your name wrong

? This user is from outside of this forum · wrote on 12 Oct 2010, 15:17

with 131 replies, I think this must be the longest threaded discussion in devnet forum so far !!!
congrats to you guys for sticking till the end and solving it :)

doforumda · wrote on 13 Oct 2010, 15:52

hi
i have got the same problem again after restarting my system.
when i execute code it again fails to connect. it returns this problem.
@
Starting /home/zafar/c++/insertquery-build-desktop/insertquery...
DB could be opened QSqlError(2002, "QMYSQL: Unable to connect", "Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2)")
/home/zafar/c++/insertquery-build-desktop/insertquery exited with code 0
@

i ran this command
@
sudo ln -s /opt/lampp/var/mysql/mysql.sock /var/run/mysqld/mysqld.sock
@
but this displays this error
@
ln: creating symbolic link `/var/run/mysqld/mysqld.sock': No such file or directory
@
i have already created this directory while lyut and Dii were solving this problem. at that time when i ran this command it worked really perfect but now it is not working.
Please help

Dii · wrote on 13 Oct 2010, 17:02

Welcome back :)

Let's check to existence of those sock files...

sudo ls -l /opt/lampp/var/mysql/mysql.sock

sudo ls -l /var/run/mysqld/mysqld.sock

doforumda · wrote on 13 Oct 2010, 17:13

well mysql.sock is there
but there is no such thing in mysqld. i mean there is no mysqld.sock file in mysqld folder

doforumda · wrote on 13 Oct 2010, 17:15

thank god your are here

doforumda · wrote on 13 Oct 2010, 17:40

i am waiting for help Dii

Dii · wrote on 13 Oct 2010, 19:50

hmmm pretty strange, does /var/run/mysqld exits? if you try

sudo mkdir /var/run/mysqld

and then the

sudo ln -s /opt/lampp/var/mysql/mysql.sock /var/run/mysqld/mysqld.sock

Though restart should not delete the directory, but I can't imagine anything else at the moment.

doforumda · wrote on 13 Oct 2010, 20:12

it works now thanks again. any clue what happened to this file after restarting.

Dii · wrote on 13 Oct 2010, 20:20

Hmmm... /var/run will be clear on each start, so you have to do a directory and the symlink again. You can do it with a script.

Or get rid of the whole LAMPP setup and use the regular mysql package. Maybe it's possible to run two mysql parallel, but I don't recommend that, too confusing.

lyuts · wrote on 14 Oct 2010, 06:01

If the problems after restart persists, then I think it will be time to change socket parameter in my.cnf. configs are created for changing settings and I don't think it will harm any component in lampp, because if it would then 1) a special note must have been written somewhere and 2) it makes no sense to allow user to change this setting if it breaks lampp.