帮助需要sql查询，选择每个类别的最新5个列表 [英] help need for sql query, select latest 5 lists of each category

问题描述

我正在使用 MySQL，我有一个包含项目和 5 个类别的数据库表(还有一个 ID 字段，autoincr，PK)我必须选择每个类别的最新 5 个项目，当我使用 group by 时它返回最新的一个项目每个类别，如何在单个查询中获得每个类别的前 5 个项目?

I am using MySQL, I have a database table with items and 5 categories(also one ID field, autoincr,PK) I have to select latest 5 items of each category, when I use group by it return latest one item of each category, how can I get top 5 items of each category in a single query ?

谢谢

推荐答案

你肯定会讨厌这个......

You properly going to hate this ...

(select * from items where category_id=1 order by add_date desc limit 5)
union
(select * from items where category_id=2 order by add_date desc limit 5)
union
(select * from items where category_id=3 order by add_date desc limit 5)
union
(select * from items where category_id=4 order by add_date desc limit 5)
union
(select * from items where category_id=5 order by add_date desc limit 5);

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