Get last 2 years value and oldest year SQL - sql

Question

I have the following table:
--------------------------------------------------------------
InspectYear Part Pos1 Pos2 Pos3 Pos4
--------------------------------------------------------------
2009 001 8 8 9 7
2009 002 9 7 8 6
2011 001 9 9 8 7
2011 002 7 8 6 8
2013 001 8 9 7 9
2013 002 7 7 8 8
2015 001 8 8 7 4
2015 002 7 6 9 8
The InspectYeardata will always add every 2 years for each Part.
I want to calculate the newest value on each pos# column with the previous year (Calc1). Also the newest value with the oldest value (Calc2). I want to have the following result:
---------------------------------------------------------------------
Part Pos 2009 2011 2013 2015 Calc1 Calc2
---------------------------------------------------------------------
001 Pos1 8 9 8 8 0 0
001 Pos2 8 9 9 8 -1 0
001 Pos3 9 8 7 7 0 -2
001 Pos4 7 7 9 4 -5 -3
For the pivot thing, I did the following code but don't know for the calculation:
declare #inspectyear as nvarchar(max), #query as nvarchar(max);
set #inspectyear = STUFF((select distinct ',' + quotename(InspectYear) from #t2 c
for XML path(''), type).value('.','NVARCHAR(MAX)'),1,1,'')
set #query =
';with data as
(
select inspectyear,
partno, Pos, number
from #t2
unpivot
(
number
for Pos in ([Pos1], [Pos2], [Pos3], [Pos4])
) unpvt
)
select * into ##temp
from data
pivot
(
sum(number)
for inspectyear in (' + #inspectyear + ')
) pvt
order by Part'
exec sp_executesql #query = #query;
select * from ##temp;
drop table ##temp;
From the table above, Calc1 is value on 2015 minus value on 2013.Calc2 is value on 2015 minus value on 2009.
The formula above will change when new records created on 2017. So the formula for Calc1 is always get the last 2 values on years. Calc2 will always get the newest value minus the oldest value.
Does anyone have an idea for this ?
Thank you.

Answer 1

You want to add in these 2 calculated columns as you insert into ##temp, but you need to specify what they are at the same time as you build your dynamic query. So you use the same method as you did to get the column names - you build a string.
At the top of your workings, add in another string variable, #calc:
declare #inspectyear as nvarchar(max), #calc as nvarchar(max), #query as nvarchar(max);
set #inspectyear = STUFF((select distinct ',' + quotename(InspectYear) from ##t2 c
for XML path(''), type).value('.','NVARCHAR(MAX)'),1,1,'')
select #calc = ', ' + quotename(Max(InspectYear)) + ' - ' + quotename(Max(InspectYear)-2)
+ ' as Calc1, ' + quotename(Max(InspectYear)) + ' - ' + quotename(min(InspectYear))
+ ' as Calc2' from #t2;
Then include that in your dynamic query string as follows:
set #query =
';with data as
(
select inspectyear,
partno, Pos, number
from #t2
unpivot
(
number
for Pos in ([Pos1], [Pos2], [Pos3], [Pos4])
) unpvt
)
select * ' + #calc + ' into ##temp
from data
pivot
(
sum(number)
for inspectyear in (' + #inspectyear + ')
) pvt
order by partno';
exec(#query);
This should add the extra columns to ##temp as required.