How to use CROSS APPLY in this scenario - sql-server

Question

I have a ProductStatus table as listed below. I need to list all products whose latest status is “SU”. Along with that I need to list what was the previous status of this product.
Based on referring various posts, it seems like CROSS APPLY will be suitable for this. I made an attempt as listed below but that didn’t give the expected result.
What is the best way to achieve this in SQL Server 2005 (without using subquery)?
DECLARE #ProductStatus TABLE (ProductStatusID INT, productCode VARCHAR(5), statusCode VARCHAR(2))
INSERT INTO #ProductStatus
SELECT 1,'10011','RE' --Recevied
UNION
SELECT 2,'10011','SU' --Suspended
UNION
SELECT 3,'10012','IT' -- In Transit
UNION
SELECT 4,'10012','RE' -- Received
UNION
SELECT 10,'10012','PR' -- Produced
UNION
SELECT 12,'10012','SU' -- Suspended
UNION
SELECT 14,'10013','RE' -- Recevied
UNION
SELECT 16,'10014','SU' -- Recevied
UNION
SELECT 18,'10014','RE' -- Recevied
CROSS APPLY attempt
SELECT *
FROM #ProductStatus P
CROSS APPLY
(
SELECT MAX(V.ProductStatusID) as maxVal
FROM #ProductStatus V
WHERE V.ProductCode = P.ProductCode
AND V. ProductStatusID < P.ProductStatusID
GROUP BY V.ProductCode
)ML
WHERE P.statusCode = 'SU'
EXPECTED RESULT

Answer 1

You can do this with cross apply but I think row_number() is an easier approach:
select ProductCode,
max(case when seqnum = 1 then statusCode end) as LastStatus,
max(case when seqnum = 2 then statusCode end) as PrevStatus
from (select p.*,
row_number() over (partition by ProductCode order by ProductStatusId desc) as seqnum
from #ProductStatus p
) p
group by ProductCode
having max(case when seqnum = 1 then statusCode end) = 'SU';

Answer 2

Lijo, I've structured it as a CTE so you can see how I've developed my ideas. You can refactor it as sub-queries without affecting the meaning if you are more comfortable with those.
;with MostRecentStatus as (
select
MAX(ProductStatusID) as ProductStatusID,
productCode
from #ProductStatus as p1
group by productCode
)
,MostRecentIsSU as (
select
p2.ProductStatusID,
p2.productCode,
p2.statusCode
from MostRecentStatus as mrs
inner join #ProductStatus as p2
on p2.ProductStatusID = mrs.ProductStatusID
and p2.statusCode = 'SU'
)
select
m.ProductStatusID,
m.productCode,
m.statusCode,
p3.statusCode as PrevStatus,
p3.ProductStatusID as PrevProductStatusID
from MostRecentIsSU as m
left outer join #ProductStatus as p3
on p3.productCode = m.productcode
and p3.ProductStatusID = m.ProductStatusID - 1;
Edit: ..and here's the ROW_NUMBER() version with kudos to #attila.
;with InSquence as
(
select
ProductStatusID,
productCode,
statusCode,
ROW_NUMBER() OVER(PARTITION BY productCode ORDER BY ProductStatusID desc) as Sequence
from #ProductStatus
)
,FirstIsSU as
(
select
ProductStatusID,
productCode
from InSquence
where Sequence = 1
and statusCode = 'SU'
)
,PreviousCode as
(
select
ProductStatusID,
productCode,
statusCode
from InSquence
where Sequence = 2
)
select
f.ProductStatusID,
f.productCode,
'SU' as CurrentStatus,
p.statusCode as PrevStatus,
p.ProductStatusID as PrevProductStatusID
from FirstIsSU as f
left outer join PreviousCode as p
on p.productCode = f.ProductCode;

Answer 3

Here is a convoluted solution which serves mainly to illustrate that this should probably be done using row_number() :)
SELECT
F.productCode, F.statusCode, F.productStatusID, F.PriorProductStatusID, PriorStatus.statusCode
FROM
(
SELECT
PCS.productCode, PCS.statusCode, PCS.productStatusID, MAX(PS.productStatusID) PriorProductStatusID
FROM
(
SELECT productCode, MAX(productStatusID) productStatusID
FROM #ProductStatus
GROUP BY productCode
) LatestStatus
INNER JOIN
#ProductStatus PCS
ON PCS.productCode = LatestStatus.productCode
AND PCS.productStatusID = LatestStatus.productStatusID
AND PCS.statusCode = 'SU'
LEFT OUTER JOIN
#ProductStatus PS
ON PS.productCode = PCS.productCode
AND PS.productStatusID < PCS.productStatusID
GROUP BY PCS.productCode, PCS.statusCode, PCS.productStatusID
) F
LEFT OUTER JOIN
#ProductStatus PriorStatus
ON F.productCode = PriorStatus.productCode
AND F.PriorProductStatusID = PriorStatus.ProductStatusID