flask之六 sqlachemy详解 scoped_session线程安全 基本增删改查 多对多关系建立和操作 flask-sqlalchemy的使用

一、sqlachemy(是一个orm框架)

1 orm框，可以独立出来用
2 orm执行原生sql
    生成engine(链接池)  详见上一篇博客
        engine = create_engine()
    获取链接
        conn = engine.raw_connection()
    后续就一样了

3 创建表，删除表和生成字段（不能创建数据库）
-写一个类
Base = declarative_base()
class Users(Base):
__tablename__ = 'users' # 数据库表名称
id = Column(Integer, primary_key=True) # id 主键
name = Column(String(32), index=True, nullable=False) # name列，索引，不可为空
-把被Base管理的所有表创建和删除
engine = create_engine()
Base.metadata.create_all(engine)
Base.metadata.drop_all(engine)
4 单表新增
engine = create_engine()
Connection = sessionmaker(bind=engine)
# 每次执行数据库操作时，都需要创建一个Connection
conn = Connection()
user=User(name='lqz')
conn.add(user)
conn.add_all([对象1，对象2])
# 提交
conn.commit()
con.close()


5 一对多关系建立
class Hobby(Base):
__tablename__ = 'hobby'
id = Column(Integer, primary_key=True)
caption = Column(String(50), default='篮球')
class Person(Base):
__tablename__ = 'person'
nid = Column(Integer, primary_key=True)
name = Column(String(32), index=True, nullable=True)
# hobby指的是tablename而不是类名，uselist=False
hobby_id = Column(Integer, ForeignKey("hobby.id"))

# 跟数据库无关，不会新增字段，只用于快速链表操作
# 类名，backref用于反向查询
hobby=relationship('Hobby',backref='pers')

5 一对多新增
engine = create_engine()
Connection = sessionmaker(bind=engine)
# 每次执行数据库操作时，都需要创建一个Connection
conn = Connection()
hobby=Hobby(caption='美女')
person=Person(name='lqz',hobby_id=1)
conn.add_all([hobby，person])
# 第二种方式
hobby=Hobby(caption='美女')
person=Person(name='lqz',hobby=hobby) # 通过对象来匹配hobby_id
conn.add_all([hobby，person])

# 提交
conn.commit()
con.close()

二、scoped_session线程安全

from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session
from models import Users

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/aaa", max_overflow=0, pool_size=5)
# 从连接池中拿一个链接
conn = sessionmaker(bind=engine)
session = scoped_session(conn)
# @app.route('/')
# def index():
#
#     session.add()







obj1 = Users(name="lqz")
session.add(obj1)



"""
# 线程安全，基于本地线程实现每个线程用同一个session
# 特殊的：scoped_session中有原来方法的Session中的一下方法：

public_methods = (
    '__contains__', '__iter__', 'add', 'add_all', 'begin', 'begin_nested',
    'close', 'commit', 'connection', 'delete', 'execute', 'expire',
    'expire_all', 'expunge', 'expunge_all', 'flush', 'get_bind',
    'is_modified', 'bulk_save_objects', 'bulk_insert_mappings',
    'bulk_update_mappings',
    'merge', 'query', 'refresh', 'rollback',
    'scalar'
)
"""


# 提交事务
session.commit()
# 关闭session
session.close()

三、基本增删改查

# 基本增删查改
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session
from models import Users,Person,Hobby
from sqlalchemy.sql import text

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/aaa", max_overflow=0, pool_size=5)
# 从连接池中拿一个链接
conn = sessionmaker(bind=engine)
session = scoped_session(conn)



# 增 add ，add_all

# 查询
#

# 查询Users表中id为1的第一条记录
# filter_by写等式，filter写比较
# res=session.query(Users).filter_by(id=1).first()

# res=session.query(Users).filter(Users.id<2)
# for user in res:
#     print(user.name)

# 影响的条数
# res=session.query(Users).filter_by(id=1).delete()
# res=session.query(Users).filter(Users.id>1).delete()
# print(res)


### 修改
# res是影响的行数
# res=session.query(Users).filter(Users.id > 0).update({"name" : "lqz"})
#类似于django的F查询
# synchronize_session=False 表示加字符串
# res=session.query(Users).filter(Users.id > 0).update({'name': Users.name + "099"}, synchronize_session=False)
# res=session.query(Users).filter(Users.id > 0).update({"age": Users.age + 1}, synchronize_session="evaluate")
# res=session.query(Users).filter(Users.id > 0).update({Users.age: Users.age + 1}, synchronize_session="evaluate")
# print(res)



#查询

# res=session.query(Users).all() # 查所有
# res=session.query(Users).all()[0] #取第一个
# res=session.query(Users).first() ##取第一个

# select name as xx,age form User;
# r2 = session.query(Users.name.label('xx'), Users.age).all()
# # r2 = session.query(Users.name.label('xx'), Users.age)
#
# # print(r2)
# for user in r2:
#     print(user.xx)


#filter传的是表达式，filter_by传的是参数
# r3 = session.query(Users).filter(Users.name == "lqz099").all()
# r3 = session.query(Users).filter(Users.id == 1).all()
# r4 = session.query(Users).filter_by(name='lqz').all()
# r5 = session.query(Users).filter_by(name='lqz').first()
# print(r3)


#:value 和:name 相当于占位符，用params传参数
# select * from user where id<6 and name=lqz099 order by id;
# r6 = session.query(Users).filter(text("id<:value and name=:name")).params(value=6, name='lqz099').order_by(Users.id).all()
#自定义查询sql
# r7 = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='lqz099').all()
#
# for u in r7:
#     print(u.id)


### 其它查询操作
#　条件
# ret = session.query(Users).filter_by(name='lqz').all()
#表达式，and条件连接
# ret = session.query(Users).filter(Users.id > 1, Users.name == 'lqz099').all()
# ret = session.query(Users).filter(Users.id.between(5, 6), Users.name == 'lqz099').all()

#注意下划线
# ret = session.query(Users).filter(Users.id.in_([1,3,4])).all()

#~非，除。。外
# ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all()

#二次筛选
# ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name='lqz099')))

from sqlalchemy import and_, or_
#or_包裹的都是or条件，and_包裹的都是and条件
# ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'eric')).all()
# ret = session.query(Users).filter(Users.id > 3, Users.name == 'eric').all()
# ret = session.query(Users).filter(or_(Users.id < 5, Users.name == 'lqz099')).all()

# ret = session.query(Users).filter(
#     or_(
#         Users.id < 2,
#         and_(Users.name == 'eric', Users.id > 3),
#         Users.age != 8
#     ))
# print(ret)

# 通配符，以e开头，不以e开头
# ret = session.query(Users).filter(Users.name.like('%9%')).all()
# ret = session.query(Users).filter(~Users.name.like('%9%'))

# 限制，用于分页，区间
# select *from user limit(1:4)
# select * from users limit 1,4;   从第一条数据往后取4条
# ret = session.query(Users)[0:4]
# ret = session.query(Users)[2:6]
# print(ret[0].id)



# 排序，根据name降序排列（从大到小）
# ret = session.query(Users).order_by(Users.name.desc()).all()
#第一个条件重复后，再按第二个条件升序排
# ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc())
# print(ret)


### 分组
# 分组
from sqlalchemy.sql import func
#分组之后取最大id，id之和，最小id
# select max(id),sum(id),min(id) from user group by name;
# ret = session.query(
#     func.max(Users.id),
#     func.sum(Users.id),
#     func.min(Users.id)).group_by(Users.name).all()
#haviing筛选
# select max(id),sum(id),min(id) from user group by name having min(id)>2;

# Users.objects.value(Users.name).filter().annotate(a=max(User.id),b=min(User.id)).filter(b__gt=2)
# 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（默认用forinkey关联）
# select * from person,hobby where person.hobby_id=hobby.id;
# ret = session.query(Person, Hobby).filter(Person.hobby_id == Hobby.id).all()
# # print(ret)[(person,hobby),(person,hobby)]
#
#
# for p in ret:
#     print(p[0])
#     print(p[1].caption)
#     print('-----')


#join表，默认是inner join,没有指定on的字段，默认用外键关联
# select * from Person inner join Hobby on  person.hobby_id =hobby.id;
# ret = session.query(Person).join(Hobby)
# print(ret)
# #isouter=True 外连，表示Person left join Favor，没有右连接，反过来即可
# ret = session.query(Person).join(Hobby, isouter=True)
ret = session.query(Hobby).join(Person, isouter=True)
# print(ret)


# 自己指定on条件（连表条件）,第二个参数，支持on多个条件，用and_,同上
# select * from Person left join Hobby on person.id=hobby.id
# ret = session.query(Person).join(Hobby,Person.hobby_id==Hobby.id, isouter=True)
# print(ret)
# select * from Person inner join Hobby on Person.hobby_id=Hobby.id where person.id>1 and hobby.caption='篮球'
# ret = session.query(Person).join(Hobby).filter(Person.id>1,Hobby.caption=='篮球')


# # 组合（了解）UNION 操作符用于合并两个或多个 SELECT 语句的结果集
# #union和union all的区别？
q1 = session.query(Person.name).filter(Person.nid > 2)
# q1 = session.query(Person.name).filter(Person.nid > 2).all()


# q2 = session.query(Hobby.caption).filter(Hobby.id < 2)
# ret = q1.union(q2).all()
# print(ret)

q1 = session.query(Person.name).filter(Person.nid > 2)
q2 = session.query(Hobby.caption).filter(Hobby.id < 2)
ret = q1.union_all(q2).all()
print(ret)




session.commit()
session.close()

四、多对多关系的建立

import datetime
from sqlalchemy import create_engine
from sqlalchemy.ext.declarative import declarative_base
from sqlalchemy.orm import relationship
from sqlalchemy import Column, Integer, String, Text, ForeignKey, DateTime, UniqueConstraint, Index
Base = declarative_base()


class Boy2Girl(Base):
    __tablename__ = 'boy2girl'
    id = Column(Integer, primary_key=True, autoincrement=True)
    girl_id = Column(Integer, ForeignKey('girl.id'))
    boy_id = Column(Integer, ForeignKey('boy.id'))


class Girl(Base):
    __tablename__ = 'girl'
    id = Column(Integer, primary_key=True)
    name = Column(String(64), unique=True, nullable=False)


class Boy(Base):
    __tablename__ = 'boy'

    id = Column(Integer, primary_key=True, autoincrement=True)
    name = Column(String(64), unique=True, nullable=False)

    # 与生成表结构无关，仅用于查询方便,放在哪个单表中都可以
    girls = relationship('Girl', secondary='boy2girl', backref='boys')


# engine = create_engine(
#         "mysql+pymysql://root:123@127.0.0.1:3306/aaa?charset=utf8",
#         max_overflow=0,  # 超过连接池大小外最多创建的连接
#         pool_size=5,  # 连接池大小
#         pool_timeout=30,  # 池中没有线程最多等待的时间，否则报错
#         pool_recycle=-1  # 多久之后对线程池中的线程进行一次连接的回收（重置）
#     )

# Base.metadata.create_all(engine)

4.1 基本增删改查

# 基本增删查改
from sqlalchemy.orm import sessionmaker
from sqlalchemy import create_engine
from sqlalchemy.orm import scoped_session
from models import Boy, Girl, Boy2Girl
from sqlalchemy.sql import text

engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/aaa", max_overflow=0, pool_size=5)
# 从连接池中拿一个链接
conn = sessionmaker(bind=engine)
session = scoped_session(conn)

# boy = Boy(name='lqz')
# boy2 = Boy(name='egon')
#
# girl = Girl(name='刘亦菲')
# girl2 = Girl(name='迪丽热巴')
# session.add_all([boy,boy2,girl,girl2])

# 建立关系
# b=Boy2Girl(girl_id=1,boy_id=1)
# b=Boy2Girl(girl=对象,boy=对象)
# session.add(b)

# lqz=session.query(Boy).filter(Boy.id==1).first()
# # dlrb=session.query(Girl).filter(Girl.id==2).first()
# lyf=session.query(Girl).filter(Girl.id==1).first()
#
#
# # lqz.girls=[dlrb,]
# lqz.girls.append(lyf)

# egon=session.query(Boy).filter(Boy.id==2).first()
# lyf=session.query(Girl).filter(Girl.id==1).first()
# lyf.boys.append(egon)
# session.add(lyf)

# lqz=session.query(Boy).filter(Boy.id==1).first()
# lyf=session.query(Girl).filter(Girl.id==1).first()
# print(lyf.boys)

session.commit()
session.close()

五、flask-sqlalchemy的使用

from flask import Flask
from flask_sqlalchemy import SQLAlchemy

app = Flask(__name__)
app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///example.sqlite"
db = SQLAlchemy(app)


class User(db.Model):
    id = db.Column(db.Integer, primary_key=True)
    username = db.Column(db.String, unique=True, nullable=False)
    email = db.Column(db.String, unique=True, nullable=False)


db.session.add(User(username="Flask", email="example@example.com"))
db.session.commit()

users = User.query.all()