You can modify your query to include a subquery that selects the minimum date for each item, and then use that in the main query to filter the rows. Here's an example of how you can modify your query:
SQL select
max(POQ.ITMREF_0) as [Article],
max(POQ.QTYSTU_0) as [Qty 1°arr.],
min(POQ.EXTRCPDAT_0) as [1° Receiving Date ],
max(POQ.RCPQTYSTU_0) as [1° Qty Ric. For.]
//max(POQ.YDATARCVPR_0) as [1° Date Receiving Conf.]
from xxxx.yyyy.PORDERQ POQ
INNER JOIN (SELECT ITMREF_0, min(EXTRCPDAT_0) as min_date from xxxx.yyyy.PORDERQ where POQ.QTYSTU_0-POQ.RCPQTYSTU_0 >0 and POQ.RCPCLEFLG_0 = 1 and year(POQ.YDATARCVPR_0)<>2000 group by ITMREF_0) subquery
ON POQ.ITMREF_0 = subquery.ITMREF_0 AND POQ.EXTRCPDAT_0 = subquery.min_date
where POQ.QTYSTU_0-POQ.RCPQTYSTU_0 >0 and POQ.RCPCLEFLG_0 = 1 and year(POQ.YDATARCVPR_0)<>2000
group by POQ.ITMREF_0
The subquery selects the minimum date for each item and join it with the main query, filtering only the rows with the min date of each item.
Please note that the query might require some adjustments depending on the specific structure and contents of the xxxx.yyyy.PORDERQ table.
