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sqlalchemy 大全
SQLAchemy
SQLAlchemy是Python编程语言下的一款ORM框架,该框架建立在数据库API之上,使用关系对象映射进行数据库操作,简言之便是:将对象转换成SQL,然后使用数据API执行SQL并获取执行结果。
SQLAlchemy本身无法操作数据库,其必须以来pymsql等第三方插件,Dialect用于和数据API进行交流,根据配置文件的不同调用不同的数据库API,从而实现对数据库的操作,如:
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1 2 3 4 5 6 7 8 9 10 11 12 13 | MySQL - Python mysql + mysqldb: / / <user>:<password>@<host>[:<port>] / <dbname> 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...] 更多详见:http: / / docs.sqlalchemy.org / en / latest / dialects / index.html |
注意 :
1 写入数据库表汉字时候 需要加编码 charset=utf8
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1 | engine = create_engine( ‘mysql+pymysql://root@127.0.0.1:3306/db2?charset=utf8‘ ) #1 连接已存在的数据库 |
2 查看执行输出 echo=true
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1 | engine = create_engine( ‘sqlite:///dbyuan67.db‘ , echo = True ) |
一、底层处理
使用 Engine/ConnectionPooling/Dialect 进行数据库操作,Engine使用ConnectionPooling连接数据库,然后再通过Dialect执行SQL语句。
+ View Code?
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 | #!/usr/bin/env python # -*- coding:utf-8 -*- from sqlalchemy import create_engine engine = create_engine( "mysql+pymysql://root:123@127.0.0.1:3306/t1" , max_overflow = 5 ) # 执行SQL # cur = engine.execute( # "INSERT INTO hosts (host, color_id) VALUES (‘1.1.1.22‘, 3)" # ) # 新插入行自增ID # cur.lastrowid # 执行SQL # cur = engine.execute( # "INSERT INTO hosts (host, color_id) VALUES(%s, %s)",[(‘1.1.1.22‘, 3),(‘1.1.1.221‘, 3),] # ) # 执行SQL # cur = engine.execute( # "INSERT INTO hosts (host, color_id) VALUES (%(host)s, %(color_id)s)", # host=‘1.1.1.99‘, color_id=3 # ) # 执行SQL # cur = engine.execute(‘select * from hosts‘) # 获取第一行数据 # cur.fetchone() # 获取第n行数据 # cur.fetchmany(3) # 获取所有数据 # cur.fetchall() |
二、ORM功能使用
使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 所有组件对数据进行操作。根据类创建对象,对象转换成SQL,执行SQL。
1 创建表
#!/usr/bin/env python# -*- coding:utf-8 -*-from sqlalchemy.ext.declarative import declarative_basefrom sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Indexfrom sqlalchemy.orm import sessionmaker, relationshipfrom sqlalchemy import create_engineengine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)Base = declarative_base()# 创建单表class Users(Base): __tablename__ = ‘users‘ id = Column(Integer, primary_key=True) name = Column(String(32)) extra = Column(String(16)) __table_args__ = ( UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘), Index(‘ix_id_name‘, ‘name‘, ‘extra‘), )# 一对多class Favor(Base): __tablename__ = ‘favor‘ nid = Column(Integer, primary_key=True) caption = Column(String(50), default=‘red‘, unique=True)class Person(Base): __tablename__ = ‘person‘ nid = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=True) favor_id = Column(Integer, ForeignKey("favor.nid"))# 多对多class Group(Base): __tablename__ = ‘group‘ id = Column(Integer, primary_key=True) name = Column(String(64), unique=True, nullable=False) port = Column(Integer, default=22)class Server(Base): __tablename__ = ‘server‘ id = Column(Integer, primary_key=True, autoincrement=True) hostname = Column(String(64), unique=True, nullable=False)class ServerToGroup(Base): __tablename__ = ‘servertogroup‘ nid = Column(Integer, primary_key=True, autoincrement=True) server_id = Column(Integer, ForeignKey(‘server.id‘)) group_id = Column(Integer, ForeignKey(‘group.id‘))def init_db(): Base.metadata.create_all(engine)def drop_db(): Base.metadata.drop_all(engine)
ForeignKeyConstraint([‘other_id‘], [‘othertable.other_id‘]),
注意点:
1 类的__call__方法
对象加括号 即 对象() 就调用
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1 2 | Session = sessionmaker(bind = engine) #实例化 Session对象 session = Session() # 对象加括号。 即 obj() 调用__call__方法 |
2 类的__repr__方法
当我们想要print(对象) 的时候,不想看到内存地址,而是要看对象封装的数据,比如self.name 等的值。就需要用到__repr__方法了
class Father(Base): __tablename__ = "father" id = Column(Integer,primary_key=True,nullable=False) name = Column(String(32)) age = Column(String(32)) son = relationship("Son") # 适合第二种插入数据的一对多方式 没有这条的话就需要按照第一种方式插入一对多数据 def __repr__(self): #打印对象的时候,就调用这里 ,我们可以直接打印对象 #只能return 字符串 return self.name + self.age
2、操作表
#!/usr/bin/env python# -*- coding:utf-8 -*-from sqlalchemy.ext.declarative import declarative_basefrom sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Indexfrom sqlalchemy.orm import sessionmaker, relationshipfrom sqlalchemy import create_engineengine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)Base = declarative_base()# 创建单表class Users(Base): __tablename__ = ‘users‘ id = Column(Integer, primary_key=True) name = Column(String(32)) extra = Column(String(16)) __table_args__ = ( UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘), Index(‘ix_id_name‘, ‘name‘, ‘extra‘), ) def __repr__(self): return "%s-%s" %(self.id, self.name)# 一对多class Favor(Base): __tablename__ = ‘favor‘ nid = Column(Integer, primary_key=True) caption = Column(String(50), default=‘red‘, unique=True) def __repr__(self): return "%s-%s" %(self.nid, self.caption)class Person(Base): __tablename__ = ‘person‘ nid = Column(Integer, primary_key=True) name = Column(String(32), index=True, nullable=True) favor_id = Column(Integer, ForeignKey("favor.nid")) # 与生成表结构无关,仅用于查询方便 favor = relationship("Favor", backref=‘pers‘)# 多对多class ServerToGroup(Base): __tablename__ = ‘servertogroup‘ nid = Column(Integer, primary_key=True, autoincrement=True) server_id = Column(Integer, ForeignKey(‘server.id‘)) group_id = Column(Integer, ForeignKey(‘group.id‘)) group = relationship("Group", backref=‘s2g‘) server = relationship("Server", backref=‘s2g‘)class Group(Base): __tablename__ = ‘group‘ id = Column(Integer, primary_key=True) name = Column(String(64), unique=True, nullable=False) port = Column(Integer, default=22) # group = relationship(‘Group‘,secondary=ServerToGroup,backref=‘host_list‘)class Server(Base): __tablename__ = ‘server‘ id = Column(Integer, primary_key=True, autoincrement=True) hostname = Column(String(64), unique=True, nullable=False)def init_db(): Base.metadata.create_all(engine)def drop_db(): Base.metadata.drop_all(engine)Session = sessionmaker(bind=engine)session = Session()
- 增
obj = Users(name="alex0", extra=‘sb‘)session.add(obj)session.add_all([ Users(name="alex1", extra=‘sb‘), Users(name="alex2", extra=‘sb‘),])session.commit()
- 删
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1 2 | session.query(Users). filter (Users. id > 2 ).delete() session.commit() |
- 改
session.query(Users).filter(Users.id > 2).update({"name" : "099"})session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + "099"}, synchronize_session=False)session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate")session.commit()
- 查
ret = session.query(Users).all()ret = session.query(Users.name, Users.extra).all()ret = session.query(Users).filter_by(name=‘alex‘).all()ret = session.query(Users).filter_by(name=‘alex‘).first()
- 其他
# 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 funcret = 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()
三 补充:
3.1 一对多表创建 主要是外键插入的两种方式
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 | #!/usr/bin/env python #_*_coding:utf-8_*_ import sqlalchemy 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 engine = create_engine( "mysql+pymysql://root:123456@127.0.0.1:3306/db3?charset=utf8" , max_overflow = 5 ) Base = declarative_base() # 生成一个SQLORM 基类 class Son(Base): __tablename__ = ‘son‘ id = Column(Integer,primary_key = True ) name = Column(String( 32 )) # 创建普通索引index=True age = Column(String( 32 )) # 创建唯一索引 唯不为空可以为null unique=True father_id = Column(Integer,ForeignKey( "father.id" )) # def __repr__(self): # 打印对象的时候,就调用这里 ,我们可以直接打印对象 # # 只能return 字符串 # return self.name+str(self.age) class Father(Base): __tablename__ = "father" id = Column(Integer,primary_key = True ,nullable = False ) name = Column(String( 32 )) age = Column(String( 32 )) son = relationship( "Son" ,backref = ‘father‘ ) # 适合第二种插入数据的一对多方式 没有这条的话就需要按照第一种方式插入一对多数据 # def __repr__(self): #打印对象的时候,就调用这里 ,我们可以直接打印对象 # #只能return 字符串 # return self.name + str(self.age) # 1 创建 删除 表 Base.metadata.create_all(engine) # 创建两个表 # Base.metadata.drop_all(engine) # 删除两个表 # 2 插入数据 # #这两行触发sessionmaker类下的__call__方法,return得到 Session实例,赋给变量session,所以session可以调用Session类下的add,add_all等方法 # 建立连接 Session = sessionmaker(bind = engine) session = Session() #第一种 插入一对多关系第一种方法 # f1 = Father(name="liujianzuo_1",age=22) # f2 = Father(name="liujianzuo_2",age=21) # # #先将 字典表的数据commit到数据库,否则建立多关系表的外键会报错 # session.add(f1) # session.add(f2) # session.commit() # 先提交字典表的数据 防止son表建立数据 无对应外键关联 # # # # # w1 = Son(name="little1 zuo 3",age=2,father_id=1) # w2 = Son(name="little zuo 4",age=3,father_id=2) # session.add_all([w1,w2]) # session.commit() # # 第二种 上面的relationship应用,这种不用先提交字典表 f3 = Father(name = "liujianzuo" ,age = 18 ) # # w1 = Son(name = "little1 zuo 5" ,age = 2 ,) w2 = Son(name = "little zuo 6" ,age = 3 ,) w3 = Son(name = "little zuo w3" ,age = 3 ,) # # f3.son=[w1,w2] # son的relationship作用 如果是已经有 w1 w2 对象就需要f3.son # # 如果已经创建过关系,再次添加新的关系就要 f3.son.append(w3) 不然重新赋值 到这原来的 w1 w2 为null了关系 # f3.son = [w1,w2] # session.add_all([f3,w1,w2]) #两种添加都行 session.add_all([f3]) session.commit() # 如果根据已经存储过的id的对应关系 # 就不能用 f2.son= 了,后面我们打印了f2.son字段,是一个列表,如果继续=就会把 query取出的数据 清空,重新赋值, # 这样再add——all 数据的时候我们取出的id的对应关系的那条记录就没了。故此用append f2 = session.query(Father).filter_by( id = 1 ).first() print (f2,w1,w2) # exit() # f2.son=[w1,w2] # 错误 f2.son.append(w1,w2) # session.add_all([f3,w1,w2]) session.add_all([f3]) session.commit() # 可以根据father对象查到关联的son信息是因为 relationship原因。 # son = relationship("Son",backref=‘father‘) # 而 根据son 对象查到father信息我们也需要在Son类定义如下 # father = relationship("Father",) # 但是如果我不想 就可以用backref了 # son = relationship("Son",backref=‘father‘) 这句话是将Son类也加个映射为# father = relationship("Father",) # 省去重新定义 # repr 显示 print (f3.son) # 在son下定义 __repr__ 才能打印返回对象封装的字段 for i in f3.son: # f3。son 是一个列表 print (i.name) # 单表跟连表查询 # print(session.query(Father).all()) # [liujianzuo_122, liujianzuo_221] 不加all 是sql select * from father # print(session.query(Father.name,Son.name).join(Son).all())#[(‘liujianzuo_1‘, ‘little1 zuo 3‘), (‘liujianzuo_2‘, ‘little zuo 4‘)] # 不加all 是sql select * from father # print(session.query(Father.name.label("f_name"),Son.name.label("s_name")).join(Son))# lable 是字段别名设置# 不加all 是sql select * from father ‘‘‘ 是如下语句 不加all() SELECT father.name AS f_name, son.name AS s_name FROM father JOIN son ON father.id = son.father_id ‘‘‘ # 过滤查询 filter 是模糊 == in filter_by print (session.query(Father). filter (Father. id .in_([ 1 ,])). all ()) # [liujianzuo_122] 模糊匹配id号 ,可以写多个 print (session.query(Father).filter_by( id = 2 ). all ()) # [liujianzuo_221] |
3.2 多对多 创建表 插入数据 以及注意点
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 | #!/usr/bin/env python # -*- coding:utf-8 -*- 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 # engine = create_engine(‘sqlite:///dbyuan674uu.db‘, echo=True) engine = create_engine( ‘mysql+pymysql://root:123456@127.0.0.1:3306/db1?charset=utf8‘ ) #1 连接已存在的数据库 Base = declarative_base() #2 创建ORM的基类 class Men_to_Wemon(Base): __tablename__ = ‘men_to_wemon‘ nid = Column(Integer, primary_key = True ) men_id = Column(Integer, ForeignKey( ‘men.id‘ )) women_id = Column(Integer, ForeignKey( ‘women.id‘ )) class Men(Base): __tablename__ = ‘men‘ id = Column(Integer, primary_key = True ) name = Column(String( 32 )) age = Column(String( 16 )) # gf= relationship("Women", secondary=Men_to_Wemon.__table__) class Women(Base): __tablename__ = ‘women‘ id = Column(Integer, primary_key = True ) name = Column(String( 32 )) age = Column(String( 16 )) bf = relationship( "Men" ,secondary = Men_to_Wemon.__table__,backref = ‘gf‘ ) # backref=‘gf‘ 相当于在men类定义了gf字段 # 创建表 # Base.metadata.create_all(engine) # 3 在数据库生成表 # 删除表 # Base.metadata.drop_all(engine) # 3 在数据库生成表 # 插入数据 Session = sessionmaker(bind = engine) session = Session() # 第一种 插入数据 # 数据汉字报错。。。。未 # m1=Men(name=‘alex‘,age=18) # m2=Men(name=‘xx‘,age=18) # w1=Women(name=‘ss‘,age=40) # w2=Women(name=‘cc‘,age=45) # session.add_all([m1,m2,w1,w2,]) # session.commit() # t1=Men_to_Wemon(men_id=1,women_id=2) # 插入关系 # session.add_all([t1,]) # session.commit() # 第二种插入数据 一对多又讲过 m1 = session.query(Men).filter_by( id = 2 ).first() # 查询id为2的男人 print (m1) w1 = session.query(Women). all () # 查询所有女人 为列表对象 m1.gf = w1 # 设置绑定关系 2号男跟所有女人 此时关系表2号还没绑定 如果2好已经有关系绑定。这里也不是所有women 只是某一个元素的话,就需要是m1.gf.append(w1)了,如果w1是一个列表的话就要m1.gf.extend(w1)了 session.add_all([m1,]) # 参考一对多 中的。 session.commit() # 需要注意的地方: # 1 查询时如果不加all,first等,得到的是sql语句,加上后,才是具体的结果;而all的结果是一个列表。 # 2 m1.gf是一个列表,里面存放着符合条件的对象。 # 3 filter与filter_by的区别:filter是拿键值对的参数,filter_by是拿条件判断的参数。 |
3.2.2 多对多的 主机与组
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1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 | from sqlalchemy import create_engine,and_,or_,func,Table from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String,ForeignKey from sqlalchemy.orm import sessionmaker,relationship engine = create_engine( ‘mysql+pymysql://root@127.0.0.1:3306/com?charset=utf8‘ ) Base = declarative_base() #生成一个SqlORM 基类 class HostToGroup(Base): __tablename__ = ‘host_2_group‘ nid = Column(Integer,primary_key = True ) host_id = Column(Integer,ForeignKey( "host.id" )) group_id = Column(Integer,ForeignKey( "group.id" )) class Host(Base): __tablename__ = ‘host‘ id = Column(Integer,primary_key = True ,autoincrement = True ) hostname = Column(String( 64 ),unique = True ,nullable = False ) ip_addr = Column(String( 128 ),unique = True ,nullable = False ) port = Column(Integer,default = 22 ) group = relationship( ‘Group‘ , secondary = HostToGroup.__table__, backref = ‘host_list‘ ) #group =relationship("Group",back_populates=‘host_list‘) def __repr__( self ): return "<id=%s,hostname=%s, ip_addr=%s>" % ( self . id , self .hostname, self .ip_addr) class Group(Base): __tablename__ = ‘group‘ id = Column(Integer,primary_key = True ) name = Column(String( 64 ),unique = True ,nullable = False ) # host_list=relationship(‘Host‘ ,secondary=HostToGroup.__table__,) def __repr__( self ): return "<id=%s,name=%s>" % ( self . id , self .name) Base.metadata.create_all(engine) #创建所有表结构 if __name__ = = ‘__main__‘ : SessionCls = sessionmaker(bind = engine) session = SessionCls() # # g1 = Group(name=‘g1‘) # g2 = Group(name=‘g2‘) # g3 = Group(name=‘g3‘) # g4 = Group(name=‘g4‘) # session.add_all([g1,g2,g3,g4]) # h1 = Host(hostname=‘h1‘,ip_addr=‘192.168.1.56‘) # h2 = Host(hostname=‘h2‘,ip_addr=‘192.168.1.57‘,port=10000) # h3 = Host(hostname=‘ubuntu‘,ip_addr=‘192.168.1.58‘,port=10000) # # # # session.add_all([h1,h2,h3]) # session.commit() # groups = session.query(Group).all() # h2 = session.query(Host).filter(Host.hostname==‘h2‘).first() # h2.group = groups[:-1] # print("===========>",h2.group) g4 = session.query(Group). filter (Group.name = = ‘g4‘ ).first() print (g4) obj1 = session.query(Host). filter (Host.hostname = = ‘h1‘ ).update({ ‘port‘ : 444 }) h2 = session.query(Host). filter (Host.hostname = = ‘h1‘ ).first() # g4.host_list.append(h2) # h2.group.append(g4) session.commit() |
sqlalchemy 大全
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