求sql语句

table_a:
id ip data time
1 192.168.100.1 2 2011-07
2 192.168.100.1 2 2011-07
3 192.168.100.1 3 2011-07
4 192.168.100.1 3 2011-07
5 192.168.100.2 4 2011-07
6 192.168.100.2 4 2011-07
7 192.168.100.2 4 2011-07
8 192.168.100.2 4 2011-07

想得到如下结果：
ip sum_data time
192.168.100.1 10 2011-07
192.168.100.12 16 2011-07

sql语句如何实现？？

SQL code

mysql> select ip,sum(data),time from a group by ip,time;
+---------------+-----------+---------+
| ip            | sum(data) | time    |
+---------------+-----------+---------+
| 192.168.100.1 |        10 | 2011-07 |
| 192.168.100.2 |        16 | 2011-07 |
+---------------+-----------+---------+
2 rows in set (0.01 sec)

select ip,time,sum(data) from tt group by ip,time;

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