mysql中的select语句where条件group by ,having , order by,limit的顺序及用法

-- 语法：
SELECT select_list　　　 
FROM table_name　　 
[ WHERE search_condition ]　　 
[ GROUP BY group_by_expression ]　　 
[ HAVING search_condition ]　　 
[ ORDER BY order_expression [ ASC | DESC ] ] 
[limit m,n] 
  
-- 示例：
-- limit 0,10是从第一条开始,取10条数据
select classNo  from table_name  
group by classNo   
having(avg(成绩)>70) 
order by classNo  
limit 0,10