Selecting data from mysql using qt?

doforumda

mysql query did its job its now successful but when i use qt code and try to make it run it displays same error

@
Starting /home/zafar/c++/dbExample-build-desktop/dbExample...
false
QSqlQuery::exec: database not open
/home/zafar/c++/dbExample-build-desktop/dbExample exited with code 0
@

doforumda

wait i think the query is not sucessful because it displays this message 0 rows affected
@
mysql> grant all on testTwo.* to 'root'at'localhost' identified by 'password';
Query OK, 0 rows affected (0.01 sec)
@

lyuts

Add this to your code after connecting:

@qDebug() << db.lastError().text();@

And tell us what the error is.

lyuts

[quote author="doforumda" date="1286877766"]wait i think the query is not sucessful because it displays this message 0 rows affected
@
mysql> grant all on testTwo.* to 'root'at'localhost' identified by 'password';
Query OK, 0 rows affected (0.01 sec)
@[/quote]

Did you run that command with 'password' instead of '123456'?

Dii

0 rows is just fine with the grant command... have you set the password on

@db.setPassword("password");@

?

doforumda

this is the output after adding lastError.text()
@
Starting /home/zafar/c++/dbExample-build-desktop/dbExample...
" "
false
QSqlQuery::exec: database not open
/home/zafar/c++/dbExample-build-desktop/dbExample exited with code 0
@

lyut: yes i use command with 'password' not '123456'

Dii sorry i didnt understand this db.setPassword("password");
where should i set this

lyuts

[quote author="doforumda" date="1286878193"]
lyut: yes i use command with 'password' not '123456'

Dii sorry i didnt understand this db.setPassword("password");
where should i set this[/quote]

I assume you should have specified the actual password when running that query.
@db.setPassword("password");@ should be added to your source code just where you set db options.

doforumda

i ran query again with actual password
i have already setup password in my qt code here it is
@
#include <QApplication>
#include <QtSql>

int main(int argc, char *argv[])
{
QCoreApplication a(argc, argv);

QSqlDatabase db = QSqlDatabase::addDatabase("QMYSQL");
db.setDatabaseName("testTwo");
db.setUserName("root");
db.setPassword("123456");
db.setHostName("localhost");

qDebug() << db.lastError().text();

bool ok = db.open();
qDebug() << ok;

QSqlQuery query;
query.exec&#40;"SELECT firstname,lastname FROM testTable"&#41;;
while(query.next()) {
    QString firstName = query.value(0).toString();
    QString secondName = query.value(1).toString();
    qDebug() << "First Name: " << firstName << "Last Name:" << secondName;
    qDebug() << db.lastError();
}
return 0;

}

@

Dii

db.lasterror().text() should come after line 16 (db.open()).
The password in the Qt code must be the same what you have specified in the GRANT command above.

I suspect probably, you haven't made the database and the table in mysql yet, if you go back to mysql command line, what do you get by these commands:

@SHOW databases;

USE testTwo;

SHOW tables;@

I go to dinner, be back in a few minutes :)

lyuts

You put my debug before opening the connection. Put it after.

doforumda

i changed db.lastError().text(); and place it after db.open()
this is the output
@
Starting /home/zafar/c++/dbExample-build-desktop/dbExample...
"Can't connect to local MySQL server through socket '/var/run/mysqld/mysqld.sock' (2) QMYSQL: Unable to connect"
false
QSqlQuery::exec: database not open
/home/zafar/c++/dbExample-build-desktop/dbExample exited with code 0
@

the commands in mysql displayed are here
repectively to your commands

mysql> use testTwo
Database changed
mysql> show tables
-> ;
+-------------------+
| Tables_in_testTwo |
+-------------------+
| testTable |
+-------------------+
1 row in set (0.01 sec)

@

doforumda

any clues?

lyuts

Change the 19th line to

@QSqlQuery query(db);@

doforumda

same error again

lyuts

Take a look into mysql logs to see what happens when you are trying to connect from your application.

doforumda

how can i check that mysql logs and from where?

lyuts

[quote author="doforumda" date="1286880547"]how can i check that mysql logs and from where? [/quote]

Try to find them:
@find /opt/lampp -name log -type d@

When you find the log directory, find a log for mysql and use tail utility:

@tail -f /path/to/mysql.log@

doforumda

this command didnt return something
@
root@zafar-laptop:/# find /opt/lampp -name log -type d
root@zafar-laptop:/#
@

doforumda

i have a folder inside lampp with the name logs. is it the one which your are talking about

lyuts

Solution 1:
@find /opt/lampp -name '*.log'@
This might need sudo'ing.

Solution 2:
If 1st fails then you need to find the config files for mysql (it should be located in /opt/lampp directory) and try to find out what is the location of mysql's log files.