为什么这个MySQL查询不起作用

Question

select p_product 
from (select p_product, count(p_product) 
      from rental 
      group by p_product 
      order by count(p_product) desc LIMIT 5);

  

错误：每个派生表都必须有自己的别名

Answer 1

为子查询添加别名：

select p_product
from (
    select p_product,
        count(p_product)
    from rental
    group by p_product
    order by count(p_product) desc LIMIT 5
    ) t;
------^ here

另外，你真的不需要子查询：

select p_product
from rental
group by p_product
order by count(p_product) desc LIMIT 5