Query Help Needed .

Hi pals,

I need small help.
I have a table with data as follows.


select * from test_data

c1 c2 c3
----------------------
111 4 101
122 3 101
133 2 102
144 2 103
155 1 103

Now i need to generate a new column c4 as sequence number in the output


I need to get the output something as follows

c4 c1 c2 c3
-----------------------------
1 111 4 101
2 122 3 101
1 133 2 102
1 144 2 103
2 155 1 103

The newly generated column contains sequence numbers starting from 1 and the sequence should be resetted again to 1 whenever a new c3 value is encountered(for example when the c3 value changes from 101 to 102 the sequence should be resetted to 1).

Can anyone help me out on this regard.

Thanks in advance,
franky