An example of the data you want to get from the query would have been nice.
If you just want to get the date of the first sold article, for every different article, a query like this should do the trick:
<pre>Select article_id, min(sale_date)
Group by article_id</pre>
As we don’t know your column and table names, you will need to make the necessary changes.
If that’s not what you meant, please provide a little more information, and if possible, some example data.