指出起烦恼的因，为的是了心苦不起苦。 重要（从关键字分析）： 查询语句的书写顺序和执行顺序 select ===> from ===> where ===> group by ===> having ===> order by ===> limit 查询语句的执行顺序 from ===> where ===> group by ===> having ===> select ===> order by ===> limi