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1. select count(distinct CName) from Course 2. select count(CName) from (select distinct CName from Course) as temp as可有可无。temp作为别名，若无则提示错误：1248 – Every derived table must have its own alias...

本文就和大家一起深入研究下mysql中group by与order by.下面是我模拟我的内容表 我现在需要取出每个分类中最新的内容 select * from test group by category_id order by `date` 结果如下 明显。这不是我想要的数据，原因是msyql已经的执行顺序是 引用 写的顺序：select ... from... where......

  select * from wap_content where week(created_at) = week(now) 如果你要严格要求是某一年的，那可以这样 查询一天： select * from table where to_days(column_time) = to_days(now()); select * from table where date(colu...

SELECT * FROM faq WHERE id >= ((SELECT MAX(id) FROM faq)-(SELECT MIN(id) FROM faq)) * RAND() + (SELECT MIN(id) FROM faq) LIMIT 9