Question

I have an article table that holds the current stock for each article. I need to know the last date when new stock has arrived, after running out of stock for that specific article.

The table looks like this.

+-----------+-----------------+-------+
| ArticleID |    StockDate    | Stock |
+-----------+-----------------+-------+
|         1 | 1/1/2012 10:15  |   100 |
|         1 | 2/1/2012 13:39  |   -50 |
|         1 | 2/1/2012 15:17  |   -50 |
|         1 | 4/1/2012 08:05  |   100 |
|         2 | 5/1/2012 09:48  |    50 |
|         1 | 6/1/2012 14:21  |   -25 |
|         1 | 7/1/2012 16:01  |    10 |
|         2 | 8/1/2012 13:42  |   -10 |
|         1 | 9/1/2012 09:56  |   -85 |
|         1 | 13/1/2012 08:12 |   100 |
|         1 | 13/1/2012 10:50 |   -15 |
+-----------+-----------------+-------+

The output should look like this.

+-----------+-----------------+
| ArticleID |    StockDate    |
+-----------+-----------------+
|         2 | 5/1/2012 09:48  |
|         1 | 13/1/2012 08:12 |
+-----------+-----------------+

How did i get this output? ArticleID 1 had a 100 in stock but reached 0 for the first time on 2/1/2012 15:17. Then new stock arrived and it hit 0 again at 9/1/2012 09:56. So the result should shows the first date after the last empty stock grouped by ArticleID. ArticleID 2 didn’t had a 0 point, so the first stock date is shown.

I need a result set that can be joined with other queries. So a Stored Procedure does not work for me.

Answer 1

select ArticleID,stockdate from 
(
    select t.ArticleID, t.stockdate, ROW_NUMBER() Over (partition by t.articleid order by v.articleid desc, stockdate) rn
    from yourtable t
    left join 
    (
        select ArticleID, MAX(stockdate) as msd from yourtable t1
        cross apply (select sum(stock) as stockrt from yourtable where stockdate<=t1.stockdate and ArticleID=t1.ArticleID) rt
        where stockrt = 0
        group by articleid
    ) v
    on t.ArticleID = v.ArticleID
    and t.stockdate>v.msd
) v
where rn=1