从一对多关系得到一对一结果

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10 年前已关闭。

Answer 1

怎么样：

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
           );