Try

ALTER TABLE table

ADD [Date] date;

go

UPDATE table

set [Date]= DateFromParts(cast([Year] as int), cast([Month] as int), 1);

go

/*

ALTER TABLE table

DROP COLUMN [Year], [Month];

*/

or

ALTER TABLE table

...

Try

;with

T as (

SELECT VendorCode, 1 as Seq, UnitPrice, Qty, (UnitPrice * Qty) as Total

from Sales

union

SELECT VendorCode, 2, sum(UnitPrice), sum(Qty), sum(UnitPrice * Qty)

from Sales

...