從列選擇在MySQL不同的價值

Question

想，我有一個表的命名項：

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 

在這裏，我想從項目降價的順序選擇SENDER_ID，goods_id表等沒有多行出現多次，其中包含相同的sender_id值（這裏是sender_id 2）。我用下面的查詢，但都是徒勞的：

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

結果表明所有五個元組（記錄）在遞減時間。但順序包含SENDER_ID 2的三次元組我想是顯示只有三個記錄其中一人的sender_id爲2，最高價格爲5000.我該怎麼辦？ 我的預期成果是：

sender_id goods_id 
    2   c1 
    3   b2 
    4   d1 

Answer 1

請儘量將

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 

Answer 2

獲得各組的最高價，你可以做象下面這樣：

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 3

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

你可以使用這個樣子。

Answer 4

試試這個：

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 

OR

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