mysql - mysql 查询 select * from table where image!='' order by date and with different upload user

Question

我想做一些 mysql 查询，按日期查询 5 个图像顺序，但来自 5 个不同的上传用户。

mysql数据表结构：id, user_id, image, text, date

SELECT *
FROM mytable
WHERE image!=''
GROUP BY user_id
ORDER BY date DESC 
LIMIT 5

但这GROUP BY总是导致获取user_id较早的上传图片然后制作ORDER BY date DESC，我需要由 5 个不同用户上传的新鲜 5 张图片。也许应该使用一些UNION，寻求帮助，谢谢。

Answer 1

试试这个查询

SELECT *
FROM temp
WHERE image!=''
GROUP BY user_id
HAVING date=max(date)
LIMIT 5

不确定，mysql但这适用于sybase.

Answer 2

将 INNER JOIN 与 MAX 一起使用

SELECT 
  mytable.* 
FROM
  mytable 
  INNER JOIN 
    (SELECT MAX(id) AS ID, id FROM mytable GROUP BY user_id) AS m 
    ON m.id = mytable.id 
WHERE image != '' 
GROUP BY user_id 
ORDER BY DATE DESC 
LIMIT 5 

这将获取 max(latest) id 并将其集成到外部选择