Work out how many days it took from one status to another : SQL - sql

Question

Please feast your eyes on this current structure of our DB.
Our DBA is currently away for the next two weeks, I have very limited SQL knowledge, I like to stay with the UI and middle tier.
What we are trying to figure out is how can we do the following, we need to write a query to calculate the average period (in days) all commissions have taken to transition from ‘Verified’ to ‘Paid’ for a single dealer, currently the status are
Created
Verified
Rejected
Awaiting Payment
Paid
Refunded
I think this query needs to aim directly at the Commission History Table?
I'm not sure how I would go about writing such query due to the fact my knowledge on SQL is limited...
Any help would be great.

Answer 1

Here's a method to achieve what you're after, although it might not be the most efficient. It seems to me that it's more of a one off query you are looking to run, rather than something that you're going to run on a frequent enough to impact database performance.
Test Table Setup:
CREATE TABLE Commission
(
CommissionId INT,
DealerId INT
)
CREATE TABLE CommissionHistory
(
CommissionId INT,
ActionDate DATETIME,
NewPaymentStatusId INT
)
Insert Dummy Data - 5 Commissions for 1 Dealer:
INSERT INTO dbo.Commission
( CommissionId ,
DealerId
)
VALUES ( 1 , 1 ),
( 2 , 1 ),
( 3 , 1 ),
( 4 , 1 ),
( 5 , 1 ),
INSERT INTO dbo.CommissionHistory
( CommissionId ,
ActionDate ,
NewPaymentStatusId
)
VALUES ( 1 , GETDATE() -25, 1 ),
( 1 , GETDATE() -21, 2 ),
( 1 , GETDATE() -18, 3 ),
( 1 , GETDATE() -16, 4 ),
( 1 , GETDATE() -5, 5 ),
( 2 , GETDATE() -10, 1 ),
( 2 , GETDATE() -9, 2 ),
( 2 , GETDATE() -8, 3 ),
( 2 , GETDATE() -7, 4 ),
( 2 , GETDATE() -6, 5 ),
( 3 , GETDATE() -10, 1 ),
( 3 , GETDATE() -8, 2 ),
( 3 , GETDATE() -6, 3 ),
( 3 , GETDATE() -4, 4 ),
( 3 , GETDATE() -2, 5 ),
( 3 , GETDATE() -25, 6 ),
( 4 , GETDATE() -10, 1 ),
( 4 , GETDATE() -7, 2 ),
( 4 , GETDATE() -6, 3 ),
( 4 , GETDATE() -4, 4 ),
( 4 , GETDATE() -1, 5 ),
( 5 , GETDATE() -1, 1 ),
( 5 , GETDATE() -1, 2 )
So with the dummy data, Commissions 1, 2 &, 4 are classified as valid records as they have status 2 and 5. 3 is excluded as it is refunded and 5 is excluded as it's not paid.
To generate the averages I wrote the below query:
-- set the required dealer id
DECLARE #DealerId INT = 1
-- return all CommissionId's in to a temp table that have statuses 2 and 5, but not 6
SELECT DISTINCT CommissionId
INTO #DealerCommissions
FROM dbo.CommissionHistory t1
WHERE CommissionId IN (SELECT CommissionId
FROM dbo.Commission
WHERE DealerId = #DealerId)
AND NOT EXISTS (SELECT CommissionId
FROM dbo.CommissionHistory t2
WHERE t2.NewPaymentStatusId = 6 AND t2.CommissionId = t1.CommissionId)
AND EXISTS (SELECT CommissionId
FROM dbo.CommissionHistory t2
WHERE t2.NewPaymentStatusId = 2 AND t2.CommissionId = t1.CommissionId)
AND EXISTS (SELECT CommissionId
FROM dbo.CommissionHistory t2
WHERE t2.NewPaymentStatusId = 5 AND t2.CommissionId = t1.CommissionId)
-- use the temp table to return average difference between the MIN & MAX date
;WITH cte AS (
SELECT CommissionId FROM #DealerCommissions
)
SELECT AVG(CAST(DaysToCompletion AS DECIMAL(10,8)))
FROM (
SELECT DATEDIFF(DAY, MIN(ch.ActionDate), MAX(ch.ActionDate)) DaysToCompletion
FROM cte
INNER JOIN dbo.CommissionHistory ch ON ch.CommissionId = cte.CommissionId
GROUP BY ch.CommissionId
) AS averageDays
-- remove temp table
DROP TABLE #DealerCommissions

Answer 2

For every commission in history table you could get the max verified date and min paid date, assuming paid date always later than verified date. Then you can join commission table to group by dealer id to get the average duration in days.
with comm as(
select
commissionid,
max(case NewPamentStatus when 'Verified' then ActionDate else null end) as verified_date,
min(case NewPamentStatus when 'Paid' then ActionDate else null end) as paid_date
--using max or min just incase that same status will be recorded more than one time.
from
CommissionHistory
group by
commistionid
)
select
c.DealerId,
avg(datediff(day,comm.verified_date,comm.paid_date))
from
comm
inner join
commission c
on c.commissionid = comm.commissionid
where
datediff(day,comm.verified_date,comm.paid_date)>0
-- to get rid off the commissions with paid date before the verified date or in same day
group by
c.DealerId