Iteration SQL Query? - sql

Question

I have very difficult scenario in my Oracle DB. I have a table setup as following:
ID File_route_group CollectID DeliveryID Sequence
---------- ------------ --------- ------------ --------
11483 12 123 411 1
12174 12 411 523 2
12465 12 523 611 3
12165 46 215 662 1
52462 12 266 394 4
12199 46 662 718 2
61244 12 394 980 5
Each line represents a "route" a certain file has taken and the following row (next sequence) should always have the same CollectID as the previous sequences DeliveryID.
In this example row ID 52462 is wrong. It should have collectID 611 (as row with sequence 3 have that as its deliveryID).
Is there a way to create a query that would have returned this row (with id 52462)? Like following:
ID File_route_group CollectID DeliveryID Sequence
---------- ------------ --------- ------------ --------
52462 12 266 394 4

Answer 1

WITH cte AS
( SELECT ID,
File_route_group,
CollectID,
DeliveryID,
Sequence,
LAG(DeliveryID, 1) OVER (PARTITION BY File_route_group
ORDER BY Sequence)
Previous_DeliveryID
FROM Routes
)
SELECT *
FROM cte
WHERE ( CollectID <> Previous_DeliveryID
OR CollectID IS NULL
OR Previous_DeliveryID IS NULL
)
AND Sequence > 1 ;
Tested at SQL-Fiddle

Answer 2

You can join the table with itself to represent the relation between the 'current' and the 'previous' entry:
SELECT * FROM route current_route
JOIN route last_route
ON current_route.Sequence = last_route.Sequence + 1
AND current_route.File_route_grp = last_route.File_route_grp
WHERE current_route.CollectID <> last_route.DeliveryID
Note that while the usage of LAG() proposed in the other answers is the more elegant and possibly more performant way of doing this in Oracle, this solution is more portable and also works, e.g. with MySQL and other DBMS.

Answer 3

In a derived table use the LAG function to get the PreviousDeliveryID then filter that where the CollectionId does not equal PreviousDeliveryID
SELECT ID, Customer_id, CollectID, DeliveryID, Sequence
FROM (
SELECT ID, Customer_id, CollectID, DeliveryID, Sequence, LAG(DeliveryID, 1) OVER(ORDER BY ID) AS PrevDeliveryID
FROM Routes
) AS t
WHERE t.CollectionID <> t.PrevDeliveryID