从MySQL中的列中选择不同的值
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21-12-2019 - |
题
假设,我有一个名为项目的表:
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
.
这里我想选择sender_id,goods_id以 项目 表,这样没有行不到一次,其中包含相同的sender_id值(这里sender_id 2)。我使用了以下查询,但是徒劳:
select distinct sender_id,goods_id from items where receiver_id=1 order by price desc
.
结果显示所有五元组(记录)包含包含Sender_id 2的元组在时间下降顺序。但是我想要的是只显示三个记录其中的三个记录2的Sender_ID,只有5000的最高价格。 我应该怎么办? 我的预期输出是:
sender_id goods_id
2 c1
3 b2
4 d1
. 解决方案
请尝试这个
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
. 其他提示
获得每个组的最高价格,您可以如下所示:
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
. 试试:
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
. select distinct (sender_id,goods_id) from items where receiver_id=1 order by price desc;
.
可以像这样使用。
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