Sounds like you want some logic like this:
SELECT IIF(c.column1 IS NULL AND c.column2 IS NULL,d.column3,c.column1) col1,
       IIF(c.column1 IS NULL AND c.column2 IS...

SELECT FirstName, SecondName, T.MaxPayDate Pay_Date
  FROM Employee e
 CROSS APPLY(SELECT TOP(1) Pay_Date
               FROM (SELECT MAX(Pay_Date) Pay_Date
       ...

declare @Date datetime
select @Date =DATEADD(mm, DATEDIFF(mm, 0, GETDATE()) - 2, 0)
Exec Results @Date
You can't have expressions in the calling parameters.

The optimizer will workout the best order to join the tables. So it will make no difference. However, there is a hint (FORCE ORDER) you can use to...

or this:
;WITH SAMPLE_DATA([AccountNumber],[Charge Category]) AS
(
    SELECT '00001XXA',220 UNION ALL
    SELECT '00001XXA',250 UNION ALL
    SELECT '00001XXA',360 UNION ALL
   ...

I'd use SQL Server's built in PERCENTILE_CONT function. Just call it with the numeric_literal = 0.5 and it will return...

UPDATE a
   SET a.DOC2 = b.DOC2
FROM myTable a
 CROSS APPLY(SELECT TOP(1) b.DOC2 FROM myTable b WHERE b.DOC = a.DOC ORDER BY b.VERSION) b

I think this is an equivalent query
;WITH cte as
(
    SELECT tkt.OrderHeader,a.*,sum(value) OVER (partition by tkt.orderheader,date) as Profit
      FROM dbo.[OrderDetails] ...

USE Test
GO
DECLARE @p1 AS INT = 9, @p2 AS INT = 2;
SELECT CAST(@p1 AS NUMERIC(12, 2))/ CAST(@p2 AS NUMERIC(12, 2)) ReturnResult
INTO dbo.TestDivisionReturnType;
GO
EXEC sp_help 'dbo.TestDivisionReturnType'
GO
DROP TABLE dbo.TestDivisionReturnType