MySQL - 将两行连接到两列

Question

我有两个表：user和photo。它们看起来像这样：

我需要根据user在uuid表格上执行SELECT，如果存在url和profile_photo，则返回background_photo。

这些基本上是我需要的最后一个字段（最后两个字段是从photo加入的）：

user.name，user.profile_photo_url，user.background_photo_url

WHERE user.uuid = SOME_UUID

有人可以用这句话指出我正确的方向吗？

Answer 1

SELECT user.name, photo_a.url AS profile_photo_url, photo_b.url as background_photo_url FROM user LEFT JOIN photo as photo_a ON user.profile_photo_uuid = photo_a.uuid LEFT JOIN photo as photo_b ON user.background_photo_uuid = photo_b.uuid WHERE user.uuid = SOME_ID

Answer 2

这应该对你有用

SELECT u.name,u.profile_photo_uuid,u.background_photo_url FROM user u, photo p 
WHERE u.uuid = **userid** AND 
( p.uuid = u.profile_photo_uuid  OR p.uuid = u.background_photo_url);