php - Mysql 两个表之间的多重联接

Question

我有两张 table 。第一个用于新闻，第二个用于图像。每个新闻可以有 0-3 个图像(新闻表中的 image_1、image_2、image_3 - 其 id)。现在我试图从图像表中获取所有行，但它只给我返回一行。

就像这样(但不起作用)

select news.id as nid, image_1, image_2, image_3, photos.id as pid, big, small
from news
left join photos
on image_1=photos.id, image_2=photos.id, image_3=photos.id
order by nid desc

Answer 1

甚至 @juergen 也提出了更好的选择，并指导您如何以自己的方式解决问题，但如果您仍然面临如何做的问题，那么您可以按照以下查询 -

SELECT p.id AS pid, n1.image_1, n2.image_2, n3.image_3, big, small
FROM photos AS p
LEFT JOIN news AS n1 ON n1.image_1=p.id 
LEFT JOIN news AS n2 ON n2.image_2=p.id 
LEFT JOIN news AS n3 ON n1.image_3=p.id 
ORDER BY n.id DESC;