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

Assuming SQL Server 2012 or newer...

SELECT
  *,
  LAG(col3) OVER (PARTITION BY col1 ORDER BY col2) AS col4
FROM
  yourTable

If you're on SQL Server 2008 or older...

SELECT
  *,
  (
     SELECT TOP(1) previous.col3
       FROM yourTable   AS previous
      WHERE previous.col1 = yourTable.col1
        AND previous.col2 < yourTable.col2
   ORDER BY previous.col2 DESC
  )
    AS col4
FROM
  yourTable