Running total in SQL Server isn’t calculating correctly - sql-server

Question

I am trying to achieve the following running total as shown below. Where a2013 is the number of enquiries from that month and 2013c is the running total.
Month a2013 2013C
---------------------
Jan 1 1
Feb 3 4
March 2 6
In a similar post it advised to add a partition which I have done but the returned value is still incorrect.
with years as (
select datename(month,p.enquirydate) as Month, count(*) as count,
count(case when p.enquirydate between '2013-01-01' and '2013-12-31
23:59:59.997' and EnrolmentYear ='2018' then datename(month,p.enquirydate)
else null end) as a2013,
count(case when p.enquirydate between '2014-01-01' and '2014-12-31
23:59:59.997' and EnrolmentYear ='2018' then datename(month,p.enquirydate)
else null end) as a2014,
count(case when p.enquirydate between '2015-01-01' and '2015-12-31
23:59:59.997' and EnrolmentYear ='2018' then datename(month,p.enquirydate)
else null end) as a2015,
count(case when p.txtenquirydate between '2016-01-01' and '2016-12-31
23:59:59.997' and EnrolmentYear ='2018' then datename(month,p.enquirydate)
else null end) as a2016,
count(case when p.enquirydate between '2017-01-01' and '2017-12-31
23:59:59.997' and EnrolmentYear ='2018' then datename(month,p.enquirydate)
else null end) as a2017
from customers p
group by datename(month,p.enquirydate), datepart(month,p.enquirydate)
)
select y.Month,a2013, sum(a2013) over(partition by y.month) as '2013C'
from years y
Month a2013 2013C
NULL 0 0
April 4 4
August 1 1
December 4 4
February 3 3
January 1 1
July 3 3
June 3 3
March 2 2
May 1 1
November 4 4
October 3 3
September 4 4

Answer 1

Maybe following query can help you to implement a SQL Running Sum solution on SQL Server with SUM() and UnBounded Preceding clause
I once used for a stock aging problem
declare #t as table (Id int, Month varchar(100), a2013 int)
insert into #t values
(1,NULL ,0),
(4,'April', 4 ),
(8,'August', 1 ),
(12,'December', 4 ),
(2,'February', 3 ),
(1,'January', 1 ),
(7,'July', 3 ),
(6,'June', 3 ),
(3,'March', 2 ),
(5,'May', 1 ),
(11,'November', 4 ),
(10,'October', 3 ),
(9,'September', 4 )
select
*,
sum([a2013]) over (order by Id rows unbounded preceding) as [2013c]
from #t
order by Id
As you can see the last column is showing sum of rows displayed before

Answer 2

with years as (
select DATEPART(month,enquirydate) as MonthNumber, count(*) as count,
count(case when p.enquirydate between '2013-01-01' and '2013-12-31 23:59:59.997' and EnrolmentYear ='2018' then datename(month,p.enquirydate)
else null end) as a2013,
count(case when p.enquirydate between '2014-01-01' and '2014-12-31 23:59:59.997' and EnrolmentYear ='2018' then datename(month,p.enquirydate)
else null end) as a2014,
count(case when p.enquirydate between '2015-01-01' and '2015-12-31 23:59:59.997' and EnrolmentYear ='2018' then datename(month,p.enquirydate)
else null end) as a2015,
count(case when p.enquirydate between '2016-01-01' and '2016-12-31 23:59:59.997' and EnrolmentYear ='2018' then datename(month,p.enquirydate)
else null end) as a2016,
count(case when p.enquirydate between '2017-01-01' and '2017-12-31 23:59:59.997' and EnrolmentYear ='2018' then datename(month,p.enquirydate)
else null end) as a2017
from #customers p
group by DATEPART(month,enquirydate)
)
select datename(month,dateadd(month, MonthNumber - 1, 0)), a2013, sum(a2013) over(Order By y.MonthNumber ROWS UNBOUNDED PRECEDING) as '2013C'
from years y