Selecting row where field = value error - php

Question

Can you explain me why my code isnt working? Ive been thinking about it for a while and I cant find it. obviously I want to print some columns from rows where column F1 is equal to user's username.
$db = JFactory::getDBO();
$user = JFactory::getUser();
$query = "SELECT * FROM qwozh_visforms_1 WHERE F1 = ".$user->username;
$db->setQuery($query);
$result = $db->query();
while($row = mysqli_fetch_object($result))
{
print $row->F1;
}
It works when I remove condition from select command and I cant figure out how to make it work with it
$query = "SELECT * FROM qwozh_visforms_1";
Now Im getting this error:
UNKNOWN COLUMN 'ADMIN' IN 'WHERE CLAUSE' SQL=SELECT * FROM
QWOZH_VISFORMS_1 WHERE F1 = ADMIN RETURN TO PREVIOUS PAGE
Thanks

Answer 1

All it takes if a quick read of the Joomla documentation. The following is the same as your query but making full use of Joomla's up to date database class:
$db = JFactory::getDbo();
$user = JFactory::getUser();
$query = $db->getQuery(true);
$query->select(array('*'))
->from($db->quoteName('#__visforms_1'))
->where($db->quoteName('F1') . ' = '. $db->quote($user->username));
$db->setQuery($query);
$results = $db->loadObjectList();
// Display the results
foreach($results as $result){
// echo what you want here
}
Note, I've used the prefix #__ rather than manually defining qwozh, assuming your table belong to a Joomla extension.

Answer 2

I know PHP and MySQL, but not Joomla. But the problem is that your username needs to be quoted because it is probably a string.
Try this:
$query = "SELECT * FROM qwozh_visforms_1 WHERE F1 = '{$user->username}'";
or
$query = "SELECT * FROM qwozh_visforms_1 WHERE F1 = ".$db->quote($user->username);

Answer 3

You need to wrap the name in quotes:
$query = "SELECT * FROM qwozh_visforms_1 WHERE F1 = '".$user->username . "'";
As pointed out in the comments my answer has a pretty bad quality, you may want to look at prepared statements, expecially using bindParam, which takes care of quotes for you and protects you agains SQL injection attacks.
Unfortunately I cannot suggest you Joomla based approach since I never used it, somebody else can suggest you a more appropriate solution.