mysql - 具有 3 种形式的内连接

Question

我收到一条错误，指出“品牌”没有唯一的表/别名，但我在 SELECT 子句中将品牌设置为 b.name，所以我不明白为什么会遇到此问题。

SELECT p.productname as product, b.name as brand

from product p, brand b, foodtype f

inner join brand
on p.brand_id = b.id
inner join foodtype
on p.foodtype_id = f.id
inner join brand
on p.petcat_id = 2
inner join brand
on p.productcat_id = pr.id

order by p.brand_id, p.product_name;

别名错误

Answer 1

建议避免使用FROM {comma list of table}，而只使用JOIN(可以使用如下别名。

SELECT p.productname as product, b.name as brand
from product p
inner join brand b
  on p.brand_id = b.id
inner join foodtype f
  on p.foodtype_id = f.id
where
  p.petcat_id = 2
order by p.brand_id, p.product_name;