mysql加入有限制吗?

本文介绍了mysql加入有限制吗?的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！ 问题描述

我有一张带有类别，产品和数量的表格.所有整数. 我正在寻找最有效的查询，该查询将为我提供每个类别的前10名产品(最高数量).

I have a table with category, product and count. All integers. I'm looking for the most efficient query that will give me the top 10 products (highest count) for each category.

我尝试了几个子选择和联接，但无法在单个查询中弄清楚该怎么做.感谢您的帮助.

I've tried several subselects and joins but couldn't figure out how to do it in a single query. Thanks for your help.

推荐答案

select a.* from t a where 10 > ( select count(*) from t b where b.category=a.category and b.count<a.count )

我认为这就是您所需要的.

I think this is what you need.