如果出现权限问题请把url里面的地址改为ip地址，不要用localhost

App和User里面的tablename对应数据库里面的表名

执行之前手动连一下postgresql数据库查看一下数据

from sqlalchemy import Column,String,create_engine
from sqlalchemy.types import CHAR,Integer,Text
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import sessionmaker
from flask import jsonify
from sqlalchemy import func
Base = declarative_base()
class App(Base):
__tablename__ = 'app'
id = Column(Integer,primary_key=True)
name = Column(String(32))
cn_name = Column(String(32))
desc = Column(Text)
status = Column(Integer)
class User(Base):
__tablename__ = 't_user'
userid = Column('userid',primary_key=True,nullable=True)
username = Column('username',String(64),nullable=True)
password = Column('password',nullable=True)


engine = create_engine('postgresql://postgres:postgres@172.17.0.37:5432/skynet',echo=True)
DBsession = sessionmaker(bind=engine)
session = DBsession()
query = session.query(App)
print session.query(func.count(App.id)).one()[0]统计多少


for i in query.all(): #列出所有
print i.id,i.name,i.cn_name,i.desc,i.status

几种常见sqlalchemy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.query(User).filter_by(name='user1').all())
print(session.query(User).filter(User.name == "user").all())
print(session.query(User).filter(User.name.like("user%")).all())

#多条件查询
print(session.query(User).filter(and_(User.name.like("user%"),User.fullname.like("first%"))).all())
print(session.query(User).filter(or_(User.name.like("user%"),User.password != None)).all())

#sql过滤
print(session.query(User).filter("id>:id").params(id=1).all())

#关联查询
print(session.query(User,Address).filter(User.id == Address.user_id).all())
print(session.query(User).join(User.addresses).all())
print(session.query(User).outerjoin(User.addresses).all())

#聚合查询
print(session.query(User.name,func.count('*').label("user_count")).group_by(User.name).all())
print(session.query(User.name,func.sum(User.id).label("user_id_sum")).group_by(User.name).all())

#子查询
stmt = session.query(Address.user_id,func.count('*').label("address_count")).group_by(Address.user_id).subquery()
print(session.query(User,stmt.c.address_count).outerjoin((stmt,User.id == stmt.c.user_id)).order_by(User.id).all())

#exists
print(session.query(User).filter(exists().where(Address.user_id == User.id)))
print(session.query(User).filter(User.addresses.any()))

限制返回字段查询
person = session.query(Person.name,Person.created_at,Person.updated_at).filter_by(name="zhongwei").order_by(Person.created_at).first()

记录总数查询： from sqlalchemy import func # count User records,without # using a subquery. session.query(func.count(User.id)) # return count of user "id" grouped # by "name" session.query(func.count(User.id)).\ group_by(User.name) from sqlalchemy import distinct # count distinct "name" values session.query(func.count(distinct(User.name)))