For Accessing Database in Joomla cms User this object
" $db = JFactory
::getDBO();".The getDBO function usually automatic create database connection.please see the below example .
For database connection use :
$db = JFactory
::getDBO();
For Execute sql or mysql query :
setQuery($query)
Example :
$query = "SELECT * FROM #__example_table WHERE id = 999999;";
$db->setQuery($query);
Fetch result from database use :
loadAssoc(): loadAssoc() returns an associated array from a single record in the table.
Example :
$db->setQuery($query);
$row = $db->loadAssoc();
print_r($row);
loadResult() : Use loadResult() when you expect just a single value back from your database query.
Example :
$db = JFactory::getDBO();
$query = "
SELECT COUNT(*)
FROM ".$db->nameQuote('#__my_table')."
WHERE ".$db->nameQuote('name')." = ".$db->quote($value).";
";
$db->setQuery($query);
$count = $db->loadResult();
loadRow(): loadRow() returns an indexed array from a single record in the table.
Example :
$db->setQuery($query);
$row = $db->loadRow();
print_r($row);
loadObject(): loadObject returns a PHP object from a single record in the table.
Example :
$db->setQuery($query);
$result = $db->loadObject();
print_r($result);
loadResultArray() : loadResultArray() returns an indexed array from a single column in the table.
Example :
$query = "
SELECT name, email, username
FROM . . . ";
. . .
$db->setQuery($query);
$column= $db->loadResultArray();
print_r($column);