Question

How do I get top 1 record for each product from the query below?

  SELECT DISTINCT o.product, o.orderID, od.qty, od.amount FROM
  orders o, orderdetails od WHERE o.orderID=od.orderID


Product  OrderID   Qty   Amount
Pen       11222    10     100.00
Pen       11223     5      50.00
Pen       11224     1      10.00
Book      22222     1      12.00
Book      2223      5      10.00
Scale     1111      2       9.00
Scale     2222      1       2.00  

Answer 1

SELECT 
    o.Product, MAX(od.QTy) 
FROM 
    orders o
    INNER JOIN orderdetails od ON o.orderID=od.orderID
GROUP BY o.Product

or

SELECT 
    o.Product, MAX(od.Amount) 
FROM 
    orders o
    INNER JOIN orderdetails od ON o.orderID=od.orderID
GROUP BY o.Product

depending on what you consider as “top” product.