python之sqlalchemy的使用

准备数据

 from sqlalchemy.ext.declarative import declarative_base
 from sqlalchemy import Column
 from sqlalchemy import Integer, String, Text, Date, DateTime, ForeignKey, UniqueConstraint, Index
 from sqlalchemy import create_engine
 from sqlalchemy.orm import relationship

 Base = declarative_base()

 class Depart(Base):
     __tablename__ = 'depart'
     id = Column(Integer, primary_key=True)
     title = Column(String(32), index=True, nullable=False)

 class Users(Base):
     __tablename__ = 'users'

     id = Column(Integer, primary_key=True)
     name = Column(String(32), index=True, nullable=False)
     depart_id = Column(Integer, ForeignKey("depart.id"))

     # 用于链表操作 与表的创建无关
     dp = relationship("Depart", backref='pers')

 class Student(Base):
     __tablename__ = 'student'
     id = Column(Integer, primary_key=True)
     name = Column(String(32), index=True, nullable=False)

     course_list = relationship('Course', secondary='student2course', backref='student_list')

 class Course(Base):
     __tablename__ = 'course'
     id = Column(Integer, primary_key=True)
     title = Column(String(32), index=True, nullable=False)

 class Student2Course(Base):
     __tablename__ = 'student2course'
     id = Column(Integer, primary_key=True, autoincrement=True)
     student_id = Column(Integer, ForeignKey('student.id'))
     course_id = Column(Integer, ForeignKey('course.id'))

     __table_args__ = (
         UniqueConstraint('student_id', 'course_id', name='uix_stu_cou'),  # 联合唯一索引
         # Index('ix_id_name', 'name', 'extra'),                          # 联合索引
     )

 def create_all():
     engine = create_engine(
         "mysql+pymysql://root:123456@192.168.226.150:3306/flask_demo?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)

 def drop_all():
     engine = create_engine(
         "mysql+pymysql://root:123456@192.168.226.150:3306/flask_demo?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.drop_all(engine)

 if __name__ == '__main__':
     # drop_all()
     create_all()

models.py

基本操作

 from sqlalchemy.orm import sessionmaker
 from sqlalchemy import create_engine
 from models import Users, Student, Depart

 engine = create_engine(
         "mysql+pymysql://root:123456@192.168.226.150:3306/flask_demo?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）
     )
 SessionFactory = sessionmaker(bind=engine)

 # 从连接池获取一个连接
 session = SessionFactory()

 # ############################## 基本增删改查 ###############################
 # 1. 增加
 obj = Users(name='tang')
 session.add(obj)
 session.commit()

 # 批量增加
 session.add_all([
         Users(name='tang'),
         Users(name='chen')
 ])
 session.commit()

 # 2. 查
 result = session.query(Users).all()
 for row in result:
         print(row.id,row.name)

 # sqlalchemy 的语法跟Python很相似
 result = session.query(Users).filter(Users.id >= 2)
 for row in result:
         print(row.id,row.name)

 # 获取第一个
 result = session.query(Users).filter(Users.id >= 2).first()
 print(result)

 # 3.删
 session.query(Users).filter(Users.id >= 2).delete()
 session.commit()

 # 4.改  通过字典
 session.query(Users).filter(Users.id == 4).update({Users.name:'tang'})
 session.query(Users).filter(Users.id == 4).update({'name':'tang'})
 session.query(Users).filter(Users.id == 4).update({'name':Users.name+"_lao"},synchronize_session=False)
 session.commit()

 # ############################## 其他常用 ###############################
 # 1. 指定列 去别名
 # 对应原生SQL：select id,name as cname from users;
 result = session.query(Users.id,Users.name.label('cname')).all()
 for item in result:
         print(item[0],item.id,item.cname)

 # 2. 默认条件and
 session.query(Users).filter(Users.id > 1, Users.name == 'eric').all()

 # 3. between
 session.query(Users).filter(Users.id.between(1, 3), Users.name == 'eric').all()

 # 4. in
 session.query(Users).filter(Users.id.in_([1,3,4])).all()
 # not in
 session.query(Users).filter(~Users.id.in_([1,3,4])).all()

 # 5. 子查询
 session.query(Users).filter(Users.id.in_(session.query(Users.id).filter(Users.name=='tang'))).all()

 # 6. and 和 or
 from sqlalchemy import and_, or_
 session.query(Users).filter(Users.id > 3, Users.name == 'tang').all()
 session.query(Users).filter(and_(Users.id > 3, Users.name == 'tang')).all()
 session.query(Users).filter(or_(Users.id < 2, Users.name == 'tang')).all()
 session.query(Users).filter(or_(Users.id < 2,and_(Users.name == 'eric', Users.id > 3),Users.extra != "")).all()

 # 7. filter_by  只需字段名
 session.query(Users).filter_by(name='alex').all()

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

 # 9. 切片
 result = session.query(Users)[1:2]

 # 10.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()

 # 11. group by
 from sqlalchemy.sql import func

 ret = session.query(Users.depart_id,func.count(Users.id),).group_by(Users.depart_id).all()
 for item in ret:
         print(item)
 #
 # from sqlalchemy.sql import func
 # 分组之后再进行查询
 ret = session.query(
         Users.depart_id,
         func.count(Users.id),
 ).group_by(Users.depart_id).having(func.count(Users.id) >= 2).all()
 for item in ret:
         print(item)

 # 12.union 和 union all
 """
 select id,name from users
 UNION
 select id,name from users;
 """
 """
 select id,name from users
 UNION ALL
 select id,name from users;
 """
 q1 = session.query(Depart.title).filter(Depart.id > 2)
 q2 = session.query(Student.name).filter(Student.id < 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()

 """
 union 和 union_all 的区别
 union 去重
 union_all 不去重

 相同点：合并的两张表的列要相同
 """

 """
 union 和 join的区别
 union是垂直合并成一张表
 join是水平合并成一张表
 """

 """
 查看原生sql 打印不获取结果的语句就可以
 sql = session.query(Users).filter(Users.id==1)
 print(sql)
 """

 session.close()

链表操作 与 外键relation字段的使用

 from sqlalchemy.orm import sessionmaker
 from sqlalchemy import create_engine
 from models import Users,Depart

 engine = create_engine(
     "mysql+pymysql://root:123456@192.168.226.150:3306/flask_demo?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）
 )

 SessionFactory = sessionmaker(bind=engine)
 session = SessionFactory()

 # 单表操作
 ret = session.query(Users).all()
 for row in ret:
     print(row.id,row.name, row.depart_id)

 # 链表操作
 ret = session.query(Users.id, Users.name, Depart.title).join(Depart,Users.depart_id==Depart.id).all()
 for row in ret:
     print(row.id, row.name, row.title)

 # isouter 表示 left join  没有right join 只能调换查询顺序
 ret = session.query(Users.id, Users.name, Depart.title).join(Users,isouter=True).all()
 # print(ret)
 for row in ret:
     print(row.id, row.name, row.title)

 # 3. relation字段:查询所有用户+所属部门名称
 ret = session.query(Users).all()
 for row in ret:
     # relation dp的作用
     print(row.id,row.name,row.depart_id, row.dp.title)

 # 4. relation字段:查询销售部所有的人员
 ret = session.query(Depart).filter(Depart.title=='销售部').first()
 for row in ret.pers:
     print(row.id, row.name, ret.title)

 # 5. 创建一个名称叫：IT部门，再在该部门中添加一个员工：tanglaoer
 u1 = Users(name='tanglaoer',dp=Depart(title='IT'))
 session.add(u1)
 session.commit()

 # 6. 创建一个名称叫：技术部，再在该部门中添加一个员工：tang lao san
 d1 = Depart(title='技术部')
 d1.pers = [Users(name='tang'),Users(name='lao'), Users(name='san')]
 session.add(d1)
 session.commit()

 # 在已存在的技术部 添加几名员工
 d1 = session.query(Depart).filter(Depart.title == '技术部').first()
 d1.pers = [Users(name='LIN'), Users(name='WU'),Users(name='SEN')]
 session.add(d1)
 session.commit()

 session.close()

Foreign and join

多对多操作

 from sqlalchemy.orm import sessionmaker
 from sqlalchemy import create_engine
 from models import Student, Course, Student2Course

 engine = create_engine(
     "mysql+pymysql://root:123456@192.168.226.150:3306/flask_demo?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）
 )

 SessionFactory = sessionmaker(bind=engine)

 session = SessionFactory()
 # 1. 录入数据
 session.add_all([
     Student(name='tang'),
     Student(name='chen'),
     Course(title='生物'),
     Course(title='体育'),
 ])
 session.commit()

 # 可批量增加多对多外键
 session.add_all([
     Student2Course(student_id=2,course_id=1),
     Student2Course(student_id=1,course_id=1),
     Student2Course(student_id=1,course_id=2),
 ])

 # 2. 三张表关联
 ret = session.query(Student2Course.id, Student.name, Course.title, Course.id).join(Student,Student2Course.student_id==Student.id).join(Course,Student2Course.course_id==Course.id).order_by(Course.id.asc()).all()
 print(ret)
 session.commit()

 # 3. “tang”选的所有课
 ret = session.query(Student2Course.id, Student.name, Course.title, Course.id).join(Student,Student2Course.student_id==Student.id).join(Course,Student2Course.course_id==Course.id).filter(Student.name=='tang').all()
 print(ret)

 # relation 字段的使用
 ret = session.query(Student).filter(Student.name== 'tang').first()
 for row in ret.course_list:
     print(row.title)

 # 4. 选了“生物”的所有人
 # relation 字段的方向使用
 ret = session.query(Course).filter(Course.title == '生物').first()
 for row in ret.student_list:
     print(row.name, ret.title)

 # 5. 创建一个课程，创建2学生，两个学生选新创建的课程。
 obj = Course(title='英语')
 obj.student_list = [Student(name='lin'), Student(name='wu')]
 session.add(obj)
 session.commit()

 # 创建一个学生，加入多门新创建课程
 stu = Student(name='tang')
 stu.course_list = [Course(title='数学'), Course(title='地理')]
 session.add(stu)
 session.commit()

 # 把tang添加到已存在的课程中
 from sqlalchemy import or_
 stu = session.query(Student).filter(Student.name=='tang').first()
 stu.course_list = session.query(Course).filter(or_(Course.id == 1, Course.id ==3)).all()
 print(stu.course_list)
 session.add(stu)
 session.commit()

 session.close()

many2many

sqlalchemy 连接与多线程的操作

 from sqlalchemy.orm import sessionmaker
 from sqlalchemy import create_engine
 from models import Student
 engine = create_engine(
     "mysql+pymysql://root:123456@192.168.226.150:3306/flask_demo?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）
 )
 SessionFactory = sessionmaker(bind=engine)

 def task():
     # 去连接池中获取一个连接
     # 第一版本
     session = SessionFactory()

     ret = session.query(Student).all()
     print(ret)
     # 将连接交还给连接池
     session.close()

 from threading import Thread

 for i in range(20):
     t = Thread(target=task)
     t.start()

第一版本

 from sqlalchemy.orm import sessionmaker
 from sqlalchemy import create_engine
 from sqlalchemy.orm import scoped_session
 from models import Student,Course,Student2Course

 engine = create_engine(
         "mysql+pymysql://root:123456@192.168.226.150:3306/flask_demo?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）
     )
 SessionFactory = sessionmaker(bind=engine)
 session = scoped_session(SessionFactory)
 # scoped_session  里面有threading.local
 # 为每个线程赋予一个连接

 def task():
     ret = session.query(Student).all()
     print(ret)
     # 将连接交还给连接池
     session.remove()

 from threading import Thread

 for i in range(20):
     t = Thread(target=task)
     t.start()

第二版本scoped_session

sqlalchemy 写原生SQL语句

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

 engine = create_engine(
         "mysql+pymysql://root:123456@192.168.226.150:3306/flask_demo?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）
     )
 SessionFactory = sessionmaker(bind=engine)
 session = scoped_session(SessionFactory)

 def task():
     """"""
     # 方式一：
     # 查询
     cursor = session.execute('select * from users')
     result = cursor.fetchall()
     print(result)

     # 添加 参数通过"冒号"
     cursor = session.execute('INSERT INTO users(name) VALUES(:value)', params={"value": 'tanglaoer'})
     session.commit()
     print(cursor.lastrowid)

     # 方式二：
     # 与pymysql的链接一模一样
     conn = engine.raw_connection()
     cursor = conn.cursor()
     cursor.execute(
         "select * from users"
     )
     result = cursor.fetchall()
     print(result)
     cursor.close()
     conn.close()

     # 将连接交还给连接池
     session.remove()

 from threading import Thread

 for i in range(20):
     t = Thread(target=task)
     t.start()

原生SQL