MySQL Query获取唯一值的计数？

Hits Table:

命中表：

hid | lid | IP
1   | 1   | 123.123.123.123
2   | 1   | 123.123.123.123
3   | 2   | 123.123.123.123
4   | 2   | 123.123.123.123
5   | 2   | 123.123.123.124
6   | 2   | 123.123.123.124
7   | 3   | 123.123.123.124
8   | 3   | 123.123.123.124
9   | 3   | 123.123.123.124
hid | lid | IP
1   | 1   |