TSQL PIVOT Function: Invalid column name error and creating calculated column - tsql

Question

I'm pretty new to the PIVOT function and I have been trying to figure this out for the past day and a half so I thought I would create an account after lurking for so long and just ask.
I have a table with the layout as follows:
AsOfDt AcctNum MntYr Dt Category Count
4/15/2015 12345 Jan-15 1/18/2015 Registered User 1
4/15/2015 12346 Feb-15 2/7/2015 New Registration User 1
4/15/2015 12347 Jan-15 1/27/2015 Unique Account 1
4/15/2015 12348 Jan-15 1/24/2015 Registered User 1
This is the end result I am trying to achieve
MntYr Account Population New Registration User Registered User Unique Account
Jan 2015 330984 12 26212 26311
Feb 2015 331897 2953 58702 58894
Mar 2015 343561 950 29498 29638
Apr 2015 343181 675 8845 8916
Grand Total 1349623 4590 123257 123759
Here is the Query that I currently have built:
WITH BaseQuery AS (
SELECT
MntYr
,Category
,[Count]
FROM [dbo].[rpt_gen_WebPortal_TestingData]
)
SELECT [MntYr]
,'Account Population'
,'Unique Account'
,'Registered User'
,'New Registration User'
FROM BaseQuery
pivot (sum([count]) for MntYr
in ("Jan 2015", "Feb 2015", "Mar 2015", "Apr 2015" )
) AS Pivoting
My first question:
I am getting an error for my MntYr column in the second SELECT statement, "Invalid column name 'MntYr'." I really don't understand why this is throwing an error. What am I doing wrong with trying to pull that column when I explicitly name it in my BaseQuery pull?
My second question:
I would also like to create a calculated field based upon the percentage of (Unique Account / Account Population), but I'm not quite sure how to go about calculated fields in a PIVOT function. Any ideas on how to get started with this one?
Any and all help would be much appreciated!
Thanks.

Answer 1

Your pivot clause was wrong. You also don't need a CTE. Try this:
SELECT
MntYr
,[Account Population]
,[Unique Account]
,[Registered User]
,[New Registration User]
,case
when isnull([Account Population],0) = 0 then 0
else 100 * [Unique Account] / [Account Population]
end Pct
FROM (
SELECT
MntYr
,Category
,[Count]
FROM [dbo].[rpt_gen_WebPortal_TestingData]
) BaseQuery
pivot (sum([Count]) for Category
in ([Account Population]
,[Unique Account]
,[Registered User]
,[New Registration User] )
) AS Pivoting