Microsoft Access查询设计

Question

SELECT 
    Item.Itemno 
    , SUM(Delivered_item.qtyordered) AS SumOfqtyordered 
    , SUM(Item_issued.qtyissued) AS SumOfqtyissued
FROM  
    Item  
    INNER JOIN Delivered_item ON Item.Itemno = Delivered_item.itemno 
    INNER JOIN Item_issued ON Item.Itemno = Item_issued.Itemno
GROUP BY  
    Item.Itemno;

This is my sql view. In my database, delivered_item has 7 records whilst item_issued only has 2 records. When I perform SUM , the total for the qtyissued gets wrong, with 1 record( qtyissued ) multiply by 3 and another record multiply by 4, due to the delivered_item having 7 records(with 2 same itemno )...how can solve this...

Answer 1

You need to use sub-queries:

SELECT *
FROM item i
INNER JOIN
  (SELECT itemno,
          Sum(qtyordered)
   FROM delivereditem
   GROUP BY itemno) d ON d.itemno = i.itemno
INNER JOIN
  (SELECT itemno,
          Sum(qtyissued)
   FROM itemissued
   GROUP BY itemno) iss ON iss.itemno = i.itemno

If you think you might have to do this a lot, turn each of the subqueries into a view and use that instead (saves on typing)

EDIT: Added the group by's in the subqueries. Sorry about that!