Question

假设我有一个名为items的表：

sender_id receiver_id goods_id price
  2            1          a1   1000
  3            1          b2   2000
  2            1          c1   5000
  4            1          d1   700
  2            1          b1   500

在这里，我想从项表中按价格的降序选择sender_id，goods_id，这样就不会出现多次包含相同sender_id值的行（这里sender_id 2）。我使用了以下查询，但是徒劳无功：

select distinct sender_id,goods_id from items where receiver_id=1 order by price desc

结果显示所有五个元组（记录）的元组包含sender_id 2三次按时间降序排列。但我想要的只显示三条记录，其中一条记录的sender_id为2，最高价格为5000 。我该怎么办？我的预期输出是：

sender_id goods_id
   2         c1
   3         b2
   4         d1

Answer 1

获得每组的最高价格，您可以这样做：

SELECT T1.*
FROM (
    SELECT
     MAX(price) AS max_price,
     sender_id
    FROM items
    GROUP BY sender_id
) AS T2
INNER JOIN items T1 ON T1.sender_id = T2.sender_id AND T1.price = T2.max_price
WHERE T1.receiver_id=1 
ORDER BY T1.price

Answer 2

试试这个：

SELECT i.sender_id, i.goods_id 
FROM items i 
INNER JOIN (SELECT i.sender_id, MAX(i.price) AS maxPrice
            FROM items i WHERE i.receiver_id=1 
            GROUP BY i.sender_id
           ) AS A ON i.sender_id = A.sender_id AND i.price = A.maxPrice
WHERE i.receiver_id=1

或

SELECT i.sender_id, i.goods_id FROM (SELECT i.sender_id, i.goods_id FROM (SELECT i.sender_id, i.goods_id FROM items i WHERE i.receiver_id=1 ORDER BY i.sender_id, i.price DESC ) AS i GROUP BY i.sender_id ) AS i

Answer 3

select distinct (sender_id,goods_id) from items where receiver_id=1 order by price desc;

你可以这样使用。

Answer 4

请试试这个

select sender_id,goods_id from items t1
where not exists (select 1 from items t2
                  where t2.sender_id = t1.sender_id
                    and t2.receiver_id = t1.receiver_id
                    and t2.price > t1.price)
 and receiver_id = 1
order by price desc

从MySql中的列中选择不同的值

4 个答案: