fix typo in comments
diff --git a/system/database/DB_query_builder.php b/system/database/DB_query_builder.php
index c9377e0..79cbfb3 100644
--- a/system/database/DB_query_builder.php
+++ b/system/database/DB_query_builder.php
@@ -1699,7 +1699,7 @@
 	 * Groups tables in FROM clauses if needed, so there is no confusion
 	 * about operator precedence.
 	 *
-	 * Note: This is only used (and overriden) by MySQL and CUBRID.
+	 * Note: This is only used (and overridden) by MySQL and CUBRID.
 	 *
 	 * @return	string
 	 */