MYSQL - 按创建日期分组2列

Question

我正在尝试在2列上使用GROUP BY获取我的表的所有结果并获得最后一次插入。

“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行，但错误的行，因为最后在我的DB -_-'

中创建

请帮帮我!!! ＆GT; _＆LT;'

THX

Answer 1

由于您在station_id子句中选择了特定WHERE，因此您无需在GROUP BY中添加该ON。

子查询必须返回您正在分组的列，然后您必须将它们包含在GROUP BY子句中。

您在外部查询中不需要JOIN，因为fuel_id应确保每个created_at只有一行（除非有重复的fuel_id对于相同的station_id和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 ）。

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