Question

I have these rows in a table

ID  Name    Price   Delivery
==  ====    =====   ========
1   apple   1       1
2   apple   3       2
3   apple   6       3
4   apple   9       4
5   orange  4       6
6   orange  5       7

I want to have the price at the third delivery (Delivery=3) or the last price if there’s no third delivery.

It would give me this :

ID  Name    Price   Delivery
==  ====    =====   ========
3   apple   6       3
6   orange  5       7

I don’t necessary want a full solution but an idea of what to look for would be greatly appreciated.

Answer 1

Use ROW_NUMBER twice – once to filter the rows away that are after the third delivery, and the second time to find the last row remaining (i.e. a typical max per group query).

I’ve implemented this using CTEs. I tested it in SQL Server but I believe that Oracle supports the same syntax.

WITH T1 AS (
    SELECT
        ID, Name, Price, Delivery,
        ROW_NUMBER() OVER (PARTITION BY Name ORDER BY Delivery) AS rn
    FROM Table1
), T2 AS (
    SELECT
        t1.*,
        ROW_NUMBER() OVER (PARTITION BY Name ORDER BY Delivery DESC) AS rn2
    FROM T1
    WHERE rn <= 3
)
SELECT ID, Name, Price, Delivery
FROM T2
WHERE rn2 = 1

Result:

ID  Name    Price  Delivery
3   apple   6      3       
6   orange  5      7