MYSQL分类取数据问题
我想每个类别只取-条数据,下面这语句执行好慢,有时好几十秒,有时又很快,是什么原因?
select t.ename,t.ntype,a.addtime,a.id,a.title from learn a inner join ntype t on t.ntypeid=a.ntypeid where a.flag=1 and 1 > (select count(id) from learn b where b.ntypeid= a.ntypeid and b.id> a.id)order by a.id desc limit 8
MYSQL里有没有类似MSSQL里的CROSS APPLY?