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'