有外鍵問題

Question

所以我的問題是在這個代碼的最底層，它說「對於查詢中的b」。目標是，如果人們對另一個人的帖子發表了評論，則將所有評論的用戶名和內容顯示給主帖。錯誤是peewee.OperationalError：沒有這樣的表：用戶。它打印i.content就好了，但是當我嘗試打印b.user.username時拋出錯誤。

import datetime 

from peewee import * 


db = SqliteDatabase('practice2.db') 


class User(Model): 
    """creates the database attributes""" 
    username = CharField(unique=True) 
    email = CharField(unique=True) 
    password = CharField(max_length=100) 
    joined_at = DateTimeField(default=datetime.datetime.now) 

    class Meta: 
     """creates the database""" 
     database = db 

class Post(Model): 
    """creates the database attributes""" 
    timestamp = DateField(default=datetime.date.today) 
    user = ForeignKeyField(
     rel_model=User, 
     related_name='posts' 
    ) 

    title = TextField() 

    content = TextField() 

    resources_to_remember = TextField() 

    time_spent = TextField() 

    tags = TextField() 

    class Meta: 
     """creates the database""" 
     database = db 

class CommentPost(Model): 
    timestamp = DateField(default=datetime.date.today) 
    user = ForeignKeyField(
     rel_model=User, 
     related_name='user_posts' 
    ) 
    related_post = ForeignKeyField(
     rel_model = Post, 
     related_name = 'com_posts') 

    content = TextField() 


def initialize(): 
    """connects to the database""" 
    db.connect() 
    db.create_tables([User, Post, CommentPost], safe=True) 

def practice(): 
    try: 
     w = User.create(username="George", email="george@gmail.com", password="KLJSklsjdfkald") 
     f_int = User.get(username="George") 
     r = Post.create(user= f_int.id, title="My First Post", content="So yeah this is my first post I think it is good.", resources_to_remember="wikipedia", time_spent="23 minutes", tags="hobbies") 
     s = Post.create(user= f_int.id, title="My Second Post", content="So yeah this is my second post I think it is good.", resources_to_remember="brittanica", time_spent="24 minutes", tags="hobbies") 
     v = CommentPost.create(user=w.id, related_post=r.id, content="Hey, see you tomorrow.") 


    except IntegrityError: 
     pass 
    else: 
     print("it worked") 
     print("") 

    a = Post.get(Post.title=="My First Post") 
    for i in a.com_posts: 
     print(i.content) 
     query = CommentPost.select(CommentPost, User).join(User).where(CommentPost.content == i.content) 
     for b in query: 
      print(b.user.username) 
      print("") 

if __name__ == '__main__': 
    initialize() 
    practice() 

Answer 1

你忘了補充：

class Meta: 
     """creates the database""" 
     database = db 

內部類：CommentPost所以未創建。