帮助需要进行sql查询，选择每个类别的最新5个列表

Question

我正在使用MySQL，我有一个包含项目和5个类别的数据库表（也有一个ID字段，autoincr，PK）我必须选择每个项目的最新5个项目类别，当我使用group时返回每个类别的最新一个项目，如何在单个查询中获得每个类别的前五个项目？

谢谢

Answer 1

你正确地去恨这个...

(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);