MYSQL - GROUP BY 2 COLUMN ORDER BY创建日期

Question

我想通过2列的GROUP BY获取我的表的所有结果并获取最后一次插入。

“价格” 表：

我的要求：

SELECT DISTINCT p.* 
FROM prices p 
JOIN (
SELECT MAX(created_at) as "last_created" 
FROM prices 
WHERE station_id = 27210003 
GROUP BY station_id, fuel_id) as sub 
ON sub.last_created = p.created_at 
WHERE p.station_id = 27210003 
GROUP BY p.station_id, p.fuel_id 

结果是3线，但错了行，因为不是我的数据库最后创建-_-”

请帮帮我!!! > _ <'

THX

Answer 1

既然你的WHERE子句中选择特定station_id，你并不需要包括在GROUP BY。

子查询必须返回要分组的列，然后必须将它们包含在ON子句中。

而且你不需要GROUP BY在外部查询，因为JOIN应确保有只有一行每个fuel_id（除非有相同fuel_id和station_id重复created_at）。

SELECT DISTINCT p.* 
FROM prices p 
JOIN (
    SELECT fuel_id, MAX(created_at) as "last_created" 
    FROM prices 
    WHERE station_id = 27210003 
    GROUP BY fuel_id) as sub 
ON sub.last_created = p.created_at AND sub.fuel_id = p.fuel_id 
WHERE p.station_id = 27210003