Use recursive CTE to handle date logic - sql

Question

At work, one of my assignments is to calculate commission to the sales staff. One rule has been more challenging than the others.
Two sales teams A and B work together each selling different products. Team A can send leads to team B. The same customer might be send multiple times. The first time a customer (ex. lead 1)* is send a commission is paid to the salesperson in team A who created the lead. Now the customer is “locked” for the next 365 days (counting from the date lead 1 was created). Meaning that no one can get additional commission for that customer in that period by sending additional leads (ex. Lead 2 and 3 gets no commission). After the 365 days have expired. A new lead can be created and receive commission (ex. Lead 4). Then the customer is locked again for 365 days counting from the day lead 4 was created. Therefore, lead 5 gets no commission. The tricky part is to reset the date that the 365 days is counted from.
'* Reference to tables #LEADS and #DISERED result.
I have solved the problem in tSQL using a cursor, but I wonder if it was possible to use a recursive CTE instead. I have made several attempts the best one is pasted in below. The problem with my solution is, that I refer to the recursive table more than once. I have tried to fix that problem with nesting a CTE inside a CTE. That’s is not allowed. I have tried using a temporary table inside the CTE that is not allowed either. I tried several times to recode the recursive part of the CTE so that the recursive table is referenced only once, but then I am not able to get the logic to work.
I am using SQL 2008
IF OBJECT_ID('tempdb.dbo.#LEADS', 'U') IS NOT NULL
DROP TABLE #LEADS;
CREATE TABLE #LEADS (LEAD_ID INT, CUSTOMER_ID INT, LEAD_CREATED_DATE DATETIME, SALESPERSON_NAME varchar(20))
INSERT INTO #LEADS
VALUES (1, 1, '2013-09-01', 'Rasmus')
,(2, 1, '2013-11-01', 'Christian')
,(3, 1, '2014-01-01', 'Nadja')
,(4, 1, '2014-12-24', 'Roar')
,(5, 1, '2015-12-01', 'Kristian')
,(6, 2, '2014-01-05', 'Knud')
,(7, 2, '2015-01-02', 'Rasmus')
,(8, 2, '2015-01-08', 'Roar')
,(9, 2, '2016-02-05', 'Kristian')
,(10, 2, '2016-03-05', 'Casper')
SELECT *
FROM #LEADS;
IF OBJECT_ID('tempdb.dbo.#DISERED_RESULT', 'U') IS NOT NULL
DROP TABLE #DISERED_RESULT;
CREATE TABLE #DISERED_RESULT (LEAD_ID INT, DESIRED_COMMISION_RESULT CHAR(3))
INSERT INTO #DISERED_RESULT
VALUES (1, 'YES')
,(2, 'NO')
,(3, 'NO')
,(4, 'YES')
,(5, 'NO')
,(6, 'YES')
,(7, 'NO')
,(8, 'YES')
,(9, 'YES')
,(10, 'NO')
SELECT *
FROM #DISERED_RESULT;
WITH COMMISSION_CALCULATION AS
(
SELECT T1.*
,COMMISSION = 'YES'
,MIN_LEAD_CREATED_DATE AS COMMISSION_DATE
FROM #LEADS AS T1
INNER JOIN (
SELECT A.CUSTOMER_ID
,MIN(A.LEAD_CREATED_DATE) AS MIN_LEAD_CREATED_DATE
FROM #LEADS AS A
GROUP BY A.CUSTOMER_ID
) AS T2 ON T1.CUSTOMER_ID = T2.CUSTOMER_ID AND T1.LEAD_CREATED_DATE = T2.MIN_LEAD_CREATED_DATE
UNION ALL
SELECT T10.LEAD_ID
,T10.CUSTOMER_ID
,T10.LEAD_CREATED_DATE
,T10.SALESPERSON_NAME
,T10.COMMISSION
,T10.COMMISSION_DATE
FROM (SELECT ROW_NUMBER() OVER(PARTITION BY T5.CUSTOMER_ID ORDER BY T5.LEAD_CREATED_DATE ASC) AS RN
,T5.*
,T6.MAX_COMMISSION_DATE
,DATEDIFF(DAY, T6.MAX_COMMISSION_DATE, T5.LEAD_CREATED_DATE) AS ANTAL_DAGE_SIDEN_SIDSTE_COMMISSION
,CASE
WHEN DATEDIFF(DAY, T6.MAX_COMMISSION_DATE, T5.LEAD_CREATED_DATE) > 365 THEN 'YES'
ELSE 'NO'
END AS COMMISSION
,CASE
WHEN DATEDIFF(DAY, T6.MAX_COMMISSION_DATE, T5.LEAD_CREATED_DATE) > 365 THEN T5.LEAD_CREATED_DATE
ELSE NULL
END AS COMMISSION_DATE
FROM #LEADS AS T5
INNER JOIN (SELECT T4.CUSTOMER_ID
,MAX(T4.COMMISSION_DATE) AS MAX_COMMISSION_DATE
FROM COMMISSION_CALCULATION AS T4
GROUP BY T4.CUSTOMER_ID) AS T6 ON T5.CUSTOMER_ID = T6.CUSTOMER_ID
WHERE T5.LEAD_ID NOT IN (SELECT LEAD_ID FROM COMMISSION_CALCULATION)
) AS T10
WHERE RN = 1
)
SELECT *
FROM COMMISSION_CALCULATION;

Answer 1

I have made some assumptions where your description does not fully make sense as written, but the below achieves your desired result:
if object_id('tempdb.dbo.#leads', 'u') is not null
drop table #leads;
create table #leads (lead_id int, customer_id int, lead_created_date datetime, salesperson_name varchar(20))
insert into #leads
values (1, 1, '2013-09-01', 'rasmus')
,(2, 1, '2013-11-01', 'christian')
,(3, 1, '2014-01-01', 'nadja')
,(4, 1, '2014-12-24', 'roar')
,(5, 1, '2015-12-01', 'kristian')
,(6, 2, '2014-01-05', 'knud')
,(7, 2, '2015-01-02', 'rasmus')
,(8, 2, '2015-01-08', 'roar')
,(9, 2, '2016-02-05', 'kristian')
,(10, 2, '2016-03-05', 'casper')
if object_id('tempdb.dbo.#disered_result', 'u') is not null
drop table #disered_result;
create table #disered_result (lead_id int, desired_commision_result char(3))
insert into #disered_result
values (1, 'yes'),(2, 'no'),(3, 'no'),(4, 'yes'),(5, 'no'),(6, 'yes'),(7, 'no'),(8, 'yes'),(9, 'yes'),(10, 'no')
with rownum
as
(
select row_number() over (order by customer_id, lead_created_date) as rn -- This is to ensure an incremantal ordering id
,lead_id
,customer_id
,lead_created_date
,salesperson_name
from #leads
)
,cte
as
(
select rn
,lead_id
,customer_id
,lead_created_date
,salesperson_name
,'yes' as commission_result
,lead_created_date as commission_window_start
from rownum
where rn = 1
union all
select r.rn
,r.lead_id
,r.customer_id
,r.lead_created_date
,r.salesperson_name
,case when r.customer_id <> c.customer_id -- If the customer ID has changed, we are at a new commission window.
then 'yes'
else case when r.lead_created_date > dateadd(d,365,c.commission_window_start) -- This assumes the window is 365 days and not one year (ie. Leap years don't add a day)
then 'yes'
else 'no'
end
end as commission_result
,case when r.customer_id <> c.customer_id
then r.lead_created_date
else case when r.lead_created_date > dateadd(d,365,c.commission_window_start) -- This assumes the window is 365 days and not one year (ie. Leap years don't add a day)
then r.lead_created_date
else c.commission_window_start
end
end as commission_window_start
from rownum r
inner join cte c
on(r.rn = c.rn+1)
)
select lead_id
,commission_result
from cte
order by customer_id
,lead_created_date;