Add getPrefix to User Guide

Author: MGatner

user_guide_src/source/database/queries.rst

@@ -72,6 +72,10 @@ without needing to create a new connection you can use this method::
 	$db->setPrefix('newprefix');
 	$db->prefixTable('tablename'); // outputs newprefix_tablename
 
+You can get the current prefix any time with this method::
+	
+	$DBPrefix = $db->getPrefix();
+
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 Protecting identifiers
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