obtenir un à un résultat de un à plusieurs rapports [clos]

Question

ma situation est que j'ai un à plusieurs relation, comme l'ordre et OrderDetails, je dois obtenir l'ordre qui a un seul détail de la commande.

Answer 1

Que diriez-vous:

select * 
from order
where order_number in
    (select order_number
     from order_details
     group by order_number
     having count(*) = 1)

Answer 2

SELECT O1.order_number
  FROM Orders AS O1
 WHERE 1 = (
            SELECT COUNT(*)
              FROM OrderDetails AS D1
             WHERE O1.order_number = D1.order_number
           );