Question

对于这张桌子......

id  type   food     price 
--------------------------
1   veg    carrot   10    
2   veg    turnip   11
3   fruit  bramble  6
4   fruit  rasp     4
5   fruit  current  9
...

我可以为每种食物类型返回最贵的食物的最高价格......

select max(price) from tableName group by type;

但我想返回包含每种食物类型最贵食物的每行的id号。并且每种食物类型返回一行且仅一行。就是回来......

id  
----
2
5 
...

这是我真正问题的简化版。

Answer 1

SELECT id
FROM ( SELECT id, type
       FROM table
       ORDER BY price DESC) AS h
GROUP BY type

Answer 2

SELECT max(id) from
(SELECT t1.* FROM tableName t1 
JOIN (SELECT type, max(price) AS price FROM tableName GROUP BY type) t2 
ON t2.type = t1.type AND t2.price = t1.price) t3
GROUP BY userId;

Answer 3

当更多的食物具有相同的类型和价格时，这个可怕的查询将起作用我几乎不会在生产中使用它，因为这是不可维护的。

SELECT MIN(id) AS id 
FROM (
    SELECT t.id AS id, t.type
    FROM tableName t
    JOIN (
        SELECT MAX(price) AS m, type
        FROM tableName 
        GROUP BY type
    ) sub 
        ON sub.m=t.price AND sub.type=t.type
    ORDER BY id
) whatever
GROUP BY type

使用group by in并返回行的标识

3 个答案: