#关联表
followers = db.Table(‘followers‘,
db.Column(‘follower_id‘, db.Integer, db.ForeignKey(‘user.id‘)),
db.Column(‘followed_id‘, db.Integer, db.ForeignKey(‘user.id‘))
)Post.query.join(...).filter(...).order_by(...)
用户表User
| id | username |
|---|---|
| 1 | john |
| 2 | susan |
| 3 | mary |
| 4 | david |
关系表followers（当john关注susan和david时）
| follower_id | followed_id |
|---|---|
| 1 | 2 |
| 1 | 4 |
| 2 | 3 |
| 3 | 4 |
帖子表Post
| id | text | user_id |
|---|---|---|
| 1 | post from susan | 2 |
| 2 | post from mary | 3 |
| 3 | post from david | 4 |
| 4 | post from john | 1 |
#join将创建一个临时表根据参数条件组合posts和followers表的数据
#条件为被关注者的id==帖子的id，即按照被关注这的帖子ID进行对应连接
Post.query.join(followers, (followers.c.followed_id == Post.user_id))
join连接结果如下
| id | text | user_id | follower_id | followed_id |
|---|---|---|---|---|
| 1 | post from susan | 2 | 1 | 2 |
| 2 | post from mary | 3 | 2 | 3 |
| 3 | post from david | 4 | 1 | 4 |
| 3 | post from david | 4 | 3 | 4 |
#注意方法定义在用户表里，所以self表示当前用户实例
filter(followers.c.follower_id == self.id)
原文：https://www.cnblogs.com/shitianfang/p/12362525.html