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我最近才刚开始使用SQLAlchemy,但仍无法解决某些概念。

归结为基本要素,我有两个这样的表(通过Flask-SQLAlchemy):

class User(db.Model):

__tablename__ = 'users'

user_id = db.Column(db.Integer, primary_key=True)

class Posts(db.Model):

__tablename__ = 'posts'

post_id = db.Column(db.Integer, primary_key=True)

user_id = db.Column(db.Integer, db.ForeignKey('users.user_id'))

post_time = db.Column(db.DateTime)

user = db.relationship('User', backref='posts')

我将如何查询用户列表及其最新帖子(不包括无帖子的用户)。 如果使用的是SQL,则可以执行以下操作:

SELECT [whatever]

FROM posts AS p

LEFT JOIN users AS u ON u.user_id = p.user_id

WHERE p.post_time = (SELECT MAX(post_time) FROM posts WHERE user_id = u.user_id)

因此,我确切地知道“期望的” SQL可以达到我想要的效果,但是不知道如何在SQLAlchemy中“正确地”表达它。

编辑:如果很重要,我使用的是SQLAlchemy 0.6.6。

我最近才刚开始使用SQLAlchemy,但仍无法解决某些概念。归结为基本要素,我有两个这样的表(通过Flask-SQLAlchemy):class User(db.Model):__tablename__ = 'users'user_id = db.Column(db.Integer, primary_key=True)class Posts(db.Model):__tablename__ = '... from sqlalchemy import Column from sqlalchemy import and_, or_ from sqlalchemy import asc, desc from sqlalchemy import exists from sqlalchemy import func class Department(db.Model): """用户管理""" import sqlalchemy from sqlalchemy import create_engine from sqlalchemy .ext.declarative import declarative_base from sqlalchemy import Column,Integer,String from sqlalchemy .o...
如果你的表比较小的话,可以对每个id单独查询,然后组成一个list: [Shoe.query.filter_by(id=id).one() for id in my_list_of_ids] 如果你的表很大,上述查询方法会很慢。此时建议使用in条件的查询 shoes = Shoe.query.filter(Shoe.id.in_(my_list_of_ids)).all() [next(s fo...
#简单查询 print(session.query(User).all()) print(session.query(User.name, User.fullname).all()) print(session.query(User, User.name).all()) #带条件查询 ... #简单查询 print(session.query(User).all()) print(session.query(User.name, User.fullname).all()) print(session.query(User, User.name).all()) #带条件查询 print(session.qu... db.session.query().order_by(desc()).all() ## asc升序 db.session.query().order_by(desc()).all() limit (限制) db.session.query().limit().all() group_by(分组) db.session.query().group_by().all() func(聚
Python SQLAlchemy Cheatsheet : https://www. python sheets.com/notes/ python - sqlalchemy .html 官方文档:https://docs. sqlalchemy .org/en/latest/orm/tutorial.html 首先 import sqlalchemy 可以这样检查版本 sqlalchemy .__version...
def queryFilter(self,start_time,end_time,cboPayMethod,cboPayStatus,cboCashier): session = self.sesstionmk() textsql = " 1=1 and orderDateTime between '"+start_time+"' and '"+end_t...
python 报错Traceback (most recent call last): File "D:\talkbot\mods\self_chatterbot.py", line 5, in <module> chatbot = ChatBot('mybot') File "E:\ python 311\Lib\site-packages\chatterbot\chatterbot.py", line 35, in __init__ self.storage = utils.initialize_class(storage_adapter, **kwargs) File "E:\ python 311\Lib\site-packages\chatterbot\utils.py", line 54, in initialize_class return Class(*args, **kwargs) File "E:\ python 311\Lib\site-packages\chatterbot\storage\sql_storage.py", line 22, in __init__ from sqlalchemy import create_engine File "E:\ python 311\Lib\site-packages\ sqlalchemy \__init__.py", line 8, in <module> from . import util as _util # noqa File "E:\ python 311\Lib\site-packages\ sqlalchemy \util\__init__.py", line 14, in <module> from ._collections import coerce_generator_arg # noqa File "E:\ python 311\Lib\site-packages\ sqlalchemy \util\_collections.py", line 16, in <module> from .compat import binary_types File "E:\ python 311\Lib\site-packages\ sqlalchemy \util\compat.py", line 264, in <module> time_func = time.clock AttributeError: module 'time' has no attribute 'clock'