How to get previous row data in sql server

Question

I would like to get the data from previous row. I have used LAG function but did not get the expected result.

Table:-

col1  col2  col3
ABCD    1   Y
ABCD         


        

Answer 1

Thank you all for the replies. By using the lag function with partition I got the expected result. I missed to used partition previously and due to that I was getting wrong results.