Question

我有这个SQL

SELECT DISTINCT DiscountID
FROM (
   SELECT DiscountID, DateCreated
   FROM PayServiceOperations
   WHERE PayServiceTypeID = 2  
   ORDER BY DateCreated DESC
) 
 AS Discount

我知道子查询中不允许的顺序。但是我还能做什么其他方式呢？

Answer 1

使用GROUP BY：

SELECT DiscountID, MAX(DateCreated)
FROM PayServiceOperations
WHERE PayServiceTypeID = 2  
GROUP BY DiscountID;

Answer 2

只是想知道你为什么要在OrderID上使用DISTINCT时创建日期的订单的子查询。你在找这个吗？我的两分钱！

  SELECT DISTINCT DiscountID
  FROM PayServiceOperations
  WHERE PayServiceTypeID = 2 
  ORDER BY DateCreated DESC

如何选择按不同字段排序的唯一字段？

2 个答案: