如何在MySQL中实现组内前几名的输出

• 从外层查询中取出一个元组，将元组相关列的值传给内层查询
• 执行内层查询，得到子查询操作的值
• 外查询根据子查询返回的结果或结果集得到满足条件的行
• 然后外层查询取出下一个元组重复做步骤1-3，直到外层的元组全部处理完毕。

select type, variety, price
from fruits
where (
   select count(*) from fruits as f
   where f.type = fruits.type and f.price < fruits.price
) <= 1;

select count(*) from fruits as f
where f.type = fruits.type and f.price < fruits.price

select count(*) from fruits as f
where f.type = apple and f.price < 2.79

select type, variety, price
from fruits
where (
   select count(*) from fruits as f
   where f.type = apple and f.price < 2.79
) <= 1;

select type, variety, price
from fruits
where (
   select count(*) from fruits as f
   where f.type = fruits.type and f.price < fruits.price
) <= 1
order by fruits.type, fruits.price