diff --git a/libraries/joomla/application/application.php b/libraries/joomla/application/application.php
index 1b772a6468..fa322f600e 100644
--- a/libraries/joomla/application/application.php
+++ b/libraries/joomla/application/application.php
@@ -1056,7 +1056,10 @@ protected function _createSession($name)
 			// The modulus introduces a little entropy, making the flushing less accurate
 			// but fires the query less than half the time.
 			$query = $db->getQuery(true);
-			$db->setQuery('DELETE FROM ' . $query->qn('#__session') . ' WHERE ' . $query->qn('time') . ' < ' . (int) ($time - $session->getExpire()));
+			$query->delete($query->qn('#__session'))
+					->where($query->qn('time') . ' < ' . $query->q((int) ($time - $session->getExpire())));
+
+			$db->setQuery($query);
 			$db->query();
 		}
 
@@ -1087,32 +1090,37 @@ public function checkSession()
 		$user = JFactory::getUser();
 
 		$query = $db->getQuery(true);
-		$db->setQuery(
-			'SELECT ' . $query->qn('session_id') . ' FROM ' . $query->qn('#__session') . ' WHERE ' . $query->qn('session_id') . ' = ' .
-			$query->q($session->getId()),
-			0, 1
-		);
+		$query->select($query->qn('session_id'))
+				->from($query->qn('#__session'))
+				->where($query->qn('session_id') . ' = ' . $query->q($session->getId()));
+
+		$db->setQuery($query, 0, 1);
 		$exists = $db->loadResult();
 
 		// If the session record doesn't exist initialise it.
 		if (!$exists)
 		{
+			$query->clear();
 			if ($session->isNew())
 			{
-				$db->setQuery(
-					'INSERT INTO ' . $query->qn('#__session') . ' (' . $query->qn('session_id') . ', ' . $query->qn('client_id') . ', ' .
-					$query->qn('time') . ')' . ' VALUES (' . $query->q($session->getId()) . ', ' . (int) $this->getClientId() . ', ' .
-					(int) time() . ')'
-				);
+				$query->insert($query->qn('#__session'))
+						->columns($query->qn('session_id') . ', ' . $query->qn('client_id') . ', ' . $query->qn('time'))
+						->values($query->q($session->getId()) . ', ' . (int) $this->getClientId() . ', ' . $query->q((int) time()));
+				$db->setQuery($query);
 			}
 			else
 			{
-				$db->setQuery(
-					'INSERT INTO ' . $query->qn('#__session') . ' (' . $query->qn('session_id') . ', ' . $query->qn('client_id') . ', ' .
-					$query->qn('guest') . ', ' . $query->qn('time') . ', ' . $query->qn('userid') . ', ' . $query->qn('username') . ')' .
-					' VALUES (' . $query->q($session->getId()) . ', ' . (int) $this->getClientId() . ', ' . (int) $user->get('guest') . ', ' .
-					(int) $session->get('session.timer.start') . ', ' . (int) $user->get('id') . ', ' . $query->q($user->get('username')) . ')'
-				);
+				$query->insert($query->qn('#__session'))
+						->columns(
+									$query->qn('session_id') . ', ' . $query->qn('client_id') . ', ' . $query->qn('guest') . ', ' .
+									$query->qn('time') . ', ' . $query->qn('userid') . ', ' . $query->qn('username')
+						)
+						->values(
+									$query->q($session->getId()) . ', ' . (int) $this->getClientId() . ', ' . (int) $user->get('guest') . ', ' .
+									$query->q((int) $session->get('session.timer.start')) . ', ' . (int) $user->get('id') . ', ' . $query->q($user->get('username'))
+						);
+
+				$db->setQuery($query);
 			}
 
 			// If the insert failed, exit the application.
diff --git a/libraries/joomla/application/categories.php b/libraries/joomla/application/categories.php
index 98380fe6a3..62c9ed174d 100644
--- a/libraries/joomla/application/categories.php
+++ b/libraries/joomla/application/categories.php
@@ -290,7 +290,7 @@ protected function _load($id)
 		// Right join with c for category
 		$query->select('c.*');
 		$case_when = ' CASE WHEN ';
-		$case_when .= $query->charLength('c.alias');
+		$case_when .= $query->charLength('c.alias') . '!=0';
 		$case_when .= ' THEN ';
 		$c_id = $query->castAsChar('c.id');
 		$case_when .= $query->concatenate(array($c_id, 'c.alias'), ':');
diff --git a/libraries/joomla/session/storage/database.php b/libraries/joomla/session/storage/database.php
index b99842055c..bb64a29d10 100644
--- a/libraries/joomla/session/storage/database.php
+++ b/libraries/joomla/session/storage/database.php
@@ -100,12 +100,14 @@ public function write($id, $data)
 			return false;
 		}
 
+		$query = $db->getQuery(true);
+		$query->update($db->quoteName('#__session'))
+				->set($db->quoteName('data') . ' = ' . $db->quote($data))
+				->set($db->quoteName('time') . ' = ' . $db->quote((int) time()))
+				->where($db->quoteName('session_id') . ' = ' . $db->quote($id));
+
 		// Try to update the session data in the database table.
-		$db->setQuery(
-			'UPDATE ' . $db->quoteName('#__session') .
-			' SET ' . $db->quoteName('data') . ' = ' . $db->quote($data) . ',' . '	  ' . $db->quoteName('time') . ' = ' . (int) time() .
-			' WHERE ' . $db->quoteName('session_id') . ' = ' . $db->quote($id)
-		);
+		$db->setQuery($query);
 		if (!$db->query())
 		{
 			return false;
@@ -117,12 +119,13 @@ public function write($id, $data)
 		}
 		else
 		{
+			$query->clear();
+			$query->insert($db->quoteName('#__session'))
+					->columns($db->quoteName('session_id') . ', ' . $db->quoteName('data') . ', ' . $db->quoteName('time'))
+					->values($db->quote($id) . ', ' . $db->quote($data) . ', ' . $db->quote((int) time()));
+
 			// If the session does not exist, we need to insert the session.
-			$db->setQuery(
-				'INSERT INTO ' . $db->quoteName('#__session') .
-				' (' . $db->quoteName('session_id') . ', ' . $db->quoteName('data') . ', ' . $db->quoteName('time') . ')' .
-				' VALUES (' . $db->quote($id) . ', ' . $db->quote($data) . ', ' . (int) time() . ')'
-			);
+			$db->setQuery($query);
 			return (boolean) $db->query();
 		}
 	}
@@ -145,11 +148,12 @@ public function destroy($id)
 			return false;
 		}
 
+		$query = $db->getQuery(true);
+		$query->delete($db->quoteName('#__session'))
+				->where($db->quoteName('session_id') . ' = ' . $db->quote($id));
+
 		// Remove a session from the database.
-		$db->setQuery(
-			'DELETE FROM ' . $db->quoteName('#__session') .
-			' WHERE ' . $db->quoteName('session_id') . ' = ' . $db->quote($id)
-		);
+		$db->setQuery($query);
 
 		return (boolean) $db->query();
 	}
@@ -175,11 +179,12 @@ public function gc($lifetime = 1440)
 		// Determine the timestamp threshold with which to purge old sessions.
 		$past = time() - $lifetime;
 
+		$query = $db->getQuery(true);
+		$query->delete($db->quoteName('#__session'))
+				->where($db->quoteName('time') . ' < ' . $db->quote((int) $past));
+
 		// Remove expired sessions from the database.
-		$db->setQuery(
-			'DELETE FROM ' . $db->quoteName('#__session') .
-			' WHERE ' . $db->quoteName('time') . ' < ' . (int) $past
-		);
+		$db->setQuery($query);
 
 		return (boolean) $db->query();
 	}