Added a default _update() method to CI_DB_active_record
diff --git a/system/database/DB_active_rec.php b/system/database/DB_active_rec.php
index 34a88ce..22b5708 100644
--- a/system/database/DB_active_rec.php
+++ b/system/database/DB_active_rec.php
@@ -1520,6 +1520,33 @@
 	// --------------------------------------------------------------------
 
 	/**
+	 * Update statement
+	 *
+	 * Generates a platform-specific update string from the supplied data
+	 *
+	 * @param	string	the table name
+	 * @param	array	the update data
+	 * @param	array	the where clause
+	 * @param	array	the orderby clause
+	 * @param	array	the limit clause
+	 * @return	string
+	 */
+	protected function _update($table, $values, $where, $orderby = array(), $limit = FALSE)
+	{
+		foreach ($values as $key => $val)
+		{
+			$valstr[] = $key.' = '.$val;
+		}
+
+		return 'UPDATE '.$table.' SET '.implode(', ', $valstr)
+			.(($where != '' && count($where) > 0) ? ' WHERE '.implode(' ', $where) : '')
+			.(count($orderby) > 0 ? ' ORDER BY '.implode(', ', $orderby) : '')
+			.($limit ? ' LIMIT '.$limit : '');
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
 	 * Validate Update
 	 *
 	 * This method is used by both update() and get_compiled_update() to