Selecting a single value from a column in MySql

Question

Suppose I have a table named items:

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   

Here I want to select sender_id, goods_id in descending order of price from the items table , so that the row is not displayed more than once, which contains the same sender_id value (here sender_id 2). I used the following query, but was in vain:

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

The result shows all five tuples (records) with tuples containing sender_id 2 three times in decreasing order of time. But I want to display only three records, one of which has sender_id of 2 with the highest price of 5000. What should I do? My expected result:

sender_id goods_id
   2         c1
   3         b2
   4         d1

Answer 1

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

, :

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

Try the following:

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

Answer 4

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

you can use this.