I am using query for joomla.
$query = \"INSERT INTO \'#__demo\'( \'id\', \'fname\', \'mname\', \'lname\' ) VALUES ( \'$val\', \'$post[\'fname\']\', \'$post[\
For inserting the data you can use this format also in joomla 2.5 :
$data =new stdClass();
$data->id = null;
$data->field1 = 'val1';
$data->field2 = 'val2';
$data->field3 = 'val3';
$db = JFactory::getDBO();
$db->insertObject( '#__mytable', $data, id );
stdClass is a php base class from which all other classes are extended.
'id' is the name for your primary key for the connected table.