Question

我有3张大致如下表：

create table user(
    id integer primary key
)

create table post(
    id integer primary key,
    author integer,
    foreign key (author) references user(id)
)

create table user_following(
    id integer primary key,
    follower integer,
    followee integer,
    foreign key (follower) references user(id),
    foreign key (followee) references user(id)
)

这些表是由ORM框架创建的，我想使用原始SQL来获取用户followee的所有帖子，这些用户可以是多个用户。我可以在SQL中执行吗？

Answer 1

这样的东西？

select p.*
from post p
join user_following uf on p.author = uf.followee
where uf.follower = 123;

Answer 2

如果您知道关注者的ID，则以下声明将进行加入，并获得关注者的跟随者＆＃39;帖子。您可以使用任何用户ID替换数字3。

SELECT * FROM user_following AS a
    JOIN post AS b ON a.followee = b.author
    WHERE a.follower=3;

Answer 3

select posts.*
from post posts
inner join [user] u_followee on u_followee.id = posts.author
inner join user_following ufo on ufo.followee = u_followee.id
inner join [user] u_follower on ufo.follower = u_follower.id
where u_follower.id = @USER_ID_WHOSE_FOLLOWEE_POSTS_REQUIRED

SQL按ID获取所有条目

3 个答案: