pip3 install SQLAlchemy

MySQL-Python
     mysql+mysqldb://<user>:<password>@<host>[:<port>]/<dbname>

例如：
mysql+pymysql://root:123@127.0.0.1:3306/db1?charset=utf8


pymysql
    mysql+pymysql://<username>:<password>@<host>/<dbname>[?<options>]
   

MySQL-Connector
    mysql+mysqlconnector://<user>:<password>@<host>[:<port>]/<dbname>
   

cx_Oracle
    oracle+cx_oracle://user:pass@host:port/dbname[?key=value&key=value...]
    

#导入模块
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy import Column,Integer,String,ForeignKey,UniqueConstraint, Index
from sqlalchemy.orm import sessionmaker,relationship
from sqlalchemy import create_engine

Base=declarative_base()#继承Base类
#创建表单
class UserType(Base):
        __tablename__=‘usertype‘##新建表名称
        id=Column(Integer,primary_key=True,autoincrement=True)##设置表列名，类型，主键，自增
        title=Column(String(32),nullable=True,index=True)##设置表列名，类型，是否可以为空，索引

class User(Base):
        __tablename__=‘users‘##新建表名称
        id = Column(Integer, primary_key=True, autoincrement=True)
        name = Column(String(32), nullable=True, index=True)
        email = Column(String(16), unique=True)##设置表列名，类型，唯一索引
        user_type_id = Column(Integer, ForeignKey(‘usertype.id‘))#设置表列名，类型，外键
          # __table_args__ = (
          # UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘),
          # Index(‘ix_n_ex‘,‘name‘, ‘email‘,),
          # )
　　

       user_type=relationship(‘UserType‘,backref=‘xxoo‘)##设置relationship，将两个类关联，在查询User表格时，也会查询到
    # UserType表格，触发查询UserType表格是在循环遍历结果时调用UserType表格的属性
    #  设置backref为反向查询
def create_db():
    Base.metadata.create_all(engine)
def drop_db():
    Base.metadata.create_all(engine)

engine=create_engine(‘mysql+pymysql://root:123@127.0.0.1:3306/db1?charset=utf8‘,max_overflow=5)#使用第三方模块连接数据库，
#设置最大连接数
Session=sessionmaker(bind=engine)#生成一个会话
session=Session()
create_db()#创建表格

##创建一个
obj1=UserType(title=‘‘)#实例化对象
session.add(obj1)

##创建多个
objs=[
 UserType(title=‘egon‘),
 UserType(title=‘eric‘),
 UserType(title=‘aldx‘)]
 session.add_all(objs) 

session.query(UserType.id,UserType.title).filter(UserType.id>2).delete()　

# 以下两种方法都是在原来基础上操作值
session.query(UserType.id,UserType.title).filter(UserType.id>0).update({UserType.title:UserType.title+‘x‘},synchronize_session=‘False‘)
##字符串操作
session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate")
##数字类型操作

print(session.query(UserType))
user_type_list=session.query(UserType).all()##user_type_list是一个列表

user_type_list=session.query(UserType).filter(UserType.id>2)##filter是过滤
#该语句相当于where条件语句

for row in user_type_list:
     print(row.id)

#　条件
ret = session.query(Users).filter_by(name=‘alex‘).all()
ret = session.query(Users).filter(Users.id > 1, Users.name == ‘eric‘).all()
ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == ‘eric‘).all()
ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()
ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()
ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name=‘eric‘))).all()
from sqlalchemy import and_, or_
ret = session.query(Users).filter(and_(Users.id > 3, Users.name == ‘eric‘)).all()
ret = session.query(Users).filter(or_(Users.id < 2, Users.name == ‘eric‘)).all()
ret = session.query(Users).filter(
    or_(
        Users.id < 2,
        and_(Users.name == ‘eric‘, Users.id > 3),
        Users.extra != ""
    )).all()


# 通配符
ret = session.query(Users).filter(Users.name.like(‘e%‘)).all()
ret = session.query(Users).filter(~Users.name.like(‘e%‘)).all()

# 限制
ret = session.query(Users)[1:2]

# 排序
ret = session.query(Users).order_by(Users.name.desc()).all()
ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all()

# 分组
from sqlalchemy.sql import func

ret = session.query(Users).group_by(Users.extra).all()
ret = session.query(
    func.max(Users.id),
    func.sum(Users.id),
    func.min(Users.id)).group_by(Users.name).all()

ret = session.query(
    func.max(Users.id),
    func.sum(Users.id),
    func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all()

# 连表

ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()

ret = session.query(Person).join(Favor).all()

ret = session.query(Person).join(Favor, isouter=True).all()


# 组合
q1 = session.query(Users.name).filter(Users.id > 2)
q2 = session.query(Favor.caption).filter(Favor.nid < 2)
ret = q1.union(q2).all()

q1 = session.query(Users.name).filter(Users.id > 2)
q2 = session.query(Favor.caption).filter(Favor.nid < 2)
ret = q1.union_all(q2).all()