Use LAG() 
https://docs.microsoft.com/en-us/sql/t-sql/functions/lag-transact-sql

WHERE [SaleDate]>DATEADD("m",-3,GETDATE()) ?
https://docs.microsoft.com/en-us/sql/t-sql/functions/dateadd-transact-sql

Like this?

SELECT YrMo
    , OType
    , Orders
    , Total
FROM
(SELECT '13/03'AS YrMo
    , 'Sales Order' AS OType
    , 300 AS Orders
    , 15000 AS Total

Agreed. Doesn't sound terribly complicated given a proper description of what data you start with and the output desired...

What do "a", "b", "c" represent? Actual values or first value, second value, third value?

Write a query to get the below result. I need output as below

what happened when you tested the code provided by deepika0928?
What exactly is the point of your post? It's just a bunch of random-ish code... Did you try any of...

Makes me think the OP is thinking in terms of Oracle, which can do that...

People here are more than happy to help, but you have to do your homework first. If you don't at least try to solve the problem yourself (post what you...

Do the databases have exactly the same tables and records?

Oh, now I get it!  (One day, I swear I'm gonna learn how to read!)
Basically, you need two things to do this - a ForEach File Loop, and an...

"automated unmanned job" - the "processing database" would have an autoexec macro in it that kicks off the processing of the databases in some folder (uses DIR() to loop over...

"I can't use CHOOSE"? What kind of requirement is that?
You have to do it in SSRS, because you said you can't modify the underlying query. How do they suggest...

Are you allowed to create calculated fields in your report definition?
=CHOOSE(Fields!GradeLevel.Value,"Pre K","K","1st","2nd","3rd","4th","5th","6th","7th", "8th", "9th", "10th", "11th", "12th")
(You could alter it to include different messages for each...