TSQL - Replace Cursor - tsql

Question

I found in our database a cursor statement and I would like to replace it.
Declare #max_date datetime
Select #max_date = max(finished) From Payments
Declare #begin_date datetime = '2015-02-01'
Declare #end_of_last_month datetime
While #begin_date <= #max_date
Begin
SELECT #end_of_last_month = CAST(DATEADD(DAY, -1 , DATEFROMPARTS(YEAR(#begin_date),MONTH(#begin_date),1)) AS DATE) --AS end_of_last_month
Insert Into #table(Customer, ArticleTypeID, ArticleType, end_of_month, month, year)
Select Count(distinct (customerId)), prod.ArticleTypeID, at.ArticleType, #end_of_last_month, datepart(month, #end_of_last_month), datepart(year, #end_of_last_month)
From Customer cust
Inner join Payments pay ON pay.member_id = m.member_id
Inner Join Products prod ON prod.product_id = pay.product_id
Inner Join ArticleType at ON at.ArticleTypeID = prod.ArticleTypeID
Where #end_of_last_month between begin_date and expire_date
and completed = 1
Group by prod.ArticleTypeID, at.ArticleType
order by prod.ArticleTypeID, at.ArticleType
Set #begin_date = DATEADD(month, 1, #begin_date)
End
It groups all User per Month where the begin- and expire date in the actual Cursormonth.
Notes:
The user has different payment types, for e.g. 1 Month, 6 Month and so on.
Is it possible to rewrite the code - my problem is only the identification at the where clause (#end_of_last_month between begin_date and expire_date)
How can I handle this with joins or cte's?

Answer 1

What you need first, if not already is a numbers table
Using said Numbers table you can create a dynamic list of dates for "end_of_Last_Month" like so
;WITH ctexAllDates
AS (
SELECT end_of_last_month = DATEADD(DAY, -1, DATEADD(MONTH, N.N -1, #begin_date))
FROM
dbo.Numbers N
WHERE
N.N <= DATEDIFF(MONTH, #begin_date, #max_date) + 1
)
select * FROM ctexAllDates
Then combine with your query like so
;WITH ctexAllDates
AS (
SELECT end_of_last_month = DATEADD(DAY, -1, DATEADD(MONTH, N.N -1, #begin_date))
FROM
dbo.Numbers N
WHERE
N.N <= DATEDIFF(MONTH, #begin_date, #max_date) + 1
)
INSERT INTO #table
(
Customer
, ArticleTypeID
, ArticleType
, end_of_month
, month
, year
)
SELECT
COUNT(DISTINCT (customerId))
, prod.ArticleTypeID
, at.ArticleType
, A.end_of_last_month
, DATEPART(MONTH, A.end_of_last_month)
, DATEPART(YEAR, A.end_of_last_month)
FROM
Customer cust
INNER JOIN Payments pay ON pay.member_id = m.member_id
INNER JOIN Products prod ON prod.product_id = pay.product_id
INNER JOIN ArticleType at ON at.ArticleTypeID = prod.ArticleTypeID
LEFT JOIN ctexAllDates A ON A.end_of_last_month BETWEEN begin_date AND expire_date
WHERE completed = 1
GROUP BY
prod.ArticleTypeID
, at.ArticleType
, A.end_of_last_month
ORDER BY
prod.ArticleTypeID
, at.ArticleType;