mysql> SELECT REPLACE(lower('wWw.Mysql.com'), 'w', 'Ww');
+--------------------------------------------+
| REPLACE(lower('wWw.Mysql.com'), 'w', 'Ww') |
+--------------------------------------------+
| WwWwWw.mysql.com                           |
+--------------------------------------------+
1 row in set (0.03 sec)

mysql>