mysql 如何获取当前时间 前一小时的时间？

mysql> select now();            
+---------------------+
| now()               |
+---------------------+
| 2011-08-08 13:59:30 |
+---------------------+
1 row in set (0.00 sec)

mysql> select date_sub(now(), interval 1 hour);
+----------------------------------+
| date_sub(now(), interval 1 hour) |
+----------------------------------+
| 2011-08-08 12:59:31              |
+----------------------------------+
1 row in set (0.00 sec)

select DATE_ADD(Now(),INTERVAL -1 hour);
select DATE_ADD(CURRENT_TIME(),INTERVAL -1 hour);