SQLAchemy

SQLAlchemy是Python編程語(yǔ)言下的一款ORM框架，該框架建立在數(shù)據(jù)庫(kù)API之上，使用關(guān)系對(duì)象映射進(jìn)行數(shù)據(jù)庫(kù)操作，簡(jiǎn)言之便是：將對(duì)象轉(zhuǎn)換成SQL，然后使用數(shù)據(jù)API執(zhí)行SQL并獲取執(zhí)行結(jié)果。

安裝：

pip3 install SQLAlchemy SQLAlchemy本身無(wú)法操作數(shù)據(jù)庫(kù)，其必須依賴pymsql等第三方插件，Dialect（用來(lái)挑選第三方api）用于和數(shù)據(jù)API進(jìn)行交流，根據(jù)配置文件的不同調(diào)用不同的數(shù)據(jù)庫(kù)API，從而實(shí)現(xiàn)對(duì)數(shù)據(jù)庫(kù)的操作，如： 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...] ??? 更多詳見：http://docs.sqlalchemy.org/en/latest/dialects/index.html 使用 Engine/ConnectionPooling/Dialect 進(jìn)行數(shù)據(jù)庫(kù)操作，Engine使用ConnectionPooling連接數(shù)據(jù)庫(kù)，然后再通過(guò)Dialect執(zhí)行SQL語(yǔ)句。 from sqlalchemy import create_engine ?? ?? engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5) ?? # 執(zhí)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 ?? # 執(zhí)行SQL # cur = engine.execute( #???? "INSERT INTO hosts (host, color_id) VALUES(%s, %s)",[('1.1.1.22', 3),('1.1.1.221', 3),] # ) ?? ?? # 執(zhí)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 # ) ?? # 執(zhí)行SQL # cur = engine.execute('select * from hosts') # 獲取第一行數(shù)據(jù) # cur.fetchone() # 獲取第n行數(shù)據(jù) # cur.fetchmany(3) # 獲取所有數(shù)據(jù) # cur.fetchall() ORM功能使用

使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 所有組件對(duì)數(shù)據(jù)進(jìn)行操作。根據(jù)類創(chuàng)建對(duì)象，對(duì)象轉(zhuǎn)換成SQL，執(zhí)行SQL。

創(chuàng)建表單

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) #此處必須是雙引號(hào) Base = declarative_base()# 創(chuàng)建單表class Users(Base):__tablename__ = 'users'#此處就是創(chuàng)建表的表名 id = Column(Integer, primary_key=True)#此處創(chuàng)建了三列name = Column(String(32))extra = Column(String(16))__table_args__ = (UniqueConstraint('id', 'name', name='uix_id_name'), #創(chuàng)建外建Index('ix_id_name', 'name', 'extra') #創(chuàng)建索引 )def __repr__(self):#這個(gè)函數(shù)的作用是打印時(shí)期作用#直接print(ret)#就可以看到想要的結(jié)果。temp = '%s-%s-%s' % (self.id, self.name, self.extra)return temp# 一對(duì)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")) # 多對(duì)多 class Group(Base):__tablename__ = 'group' id = Column(Integer, primary_key=True) name = Column(String(64), unique=True, nullable=False) class Server(Base):__tablename__ = 'server' id = Column(Integer, primary_key=True, autoincrement=True) hostname = Column(String(64), unique=True, nullable=False)port = Column(Integer, default=22)class ServerToGroup(Base):__tablename__ = 'servertogroup'nid = Column(Integer, primary_key=True, autoincrement=True)server_id = Column(Integer, ForeignKey('server.id')) #必須要有約束，就是外鍵group_id = Column(Integer, ForeignKey('group.id'))def init_db():Base.metadata.create_all(engine)#創(chuàng)建所有表def drop_db():Base.metadata.drop_all(engine)#刪除所有表

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操作表

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_engineengine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5)Base = declarative_base()# 創(chuàng)建單表 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)# 一對(duì)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"))# 與生成表結(jié)構(gòu)無(wú)關(guān)，僅用于查詢方便favor = relationship("Favor", backref='pers') #此處的作用就是聯(lián)表，會(huì)把favor表中的數(shù)據(jù)讀出來(lái)，不用我們?nèi)懧?lián)表語(yǔ)句。必須與關(guān)聯(lián)的表中有foreignkey才可以。# backref的作用就是在favor表中加了一個(gè)pers的字段，.pers就表示與favor相關(guān)的所有信息#正向查詢 ret = session.query(Person) print(ret) for obj in ret:print(obj.nid,obj.name,obj.favor_id,obj.favor.captiom)# 反向查詢 # obj = session.query(Group).filter(Group.caption =='DBA').first() # print(obj.nid) # print(obj.caption) # print(obj.uuu) #通過(guò)查找Group中在DBA組的成員，如果relationship中的backref指定uuu，那么，.uuu就把realtionship所關(guān)聯(lián)表中的所有在DBA中的成員列出來(lái)。# 多對(duì)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) #如果想操作數(shù)據(jù)庫(kù)必須要?jiǎng)?chuàng)建這個(gè)session session = Session()

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增

obj = Users(name="alex0", extra='sb') 增加一條數(shù)據(jù)
session.add(obj) session.add_all([ 批量增加
Users(name="alex1", extra='sb'),Users(name="alex2", extra='sb'), ]) session.commit()

刪

session.query(Users).filter(Users.id > 2).delete() 如果想用and的話，就在〉2后面加，然后再跟條件
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) 字符串相加 session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate") 數(shù)字相加 session.commit()

查

ret = session.query(Users).all() 不加.all()print（ret）就會(huì)看到執(zhí)行語(yǔ)句 如果想查看的話，可以執(zhí)行：
print(ret[0].name) 因?yàn)閞et是個(gè)列表，表中有幾列，列表中就會(huì)有幾個(gè)元素。
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：

#　條件 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() 在這個(gè)范圍 ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all() 波浪號(hào)代表非 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()# 分組 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()# 連表 ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all()ret = session.query(Person).join(Favor).all() 此處的join默認(rèn)是inner joinret = session.query(Person).join(Favor, isouter=True).all() outer表示leftjoin# 組合 q1 = session.query(Users.name).filter(Users.id > 2) q2 = session.query(Favor.caption).filter(Favor.nid < 2) ret = q1.union(q2).all() 會(huì)去重q1 = session.query(Users.name).filter(Users.id > 2) q2 = session.query(Favor.caption).filter(Favor.nid < 2) ret = q1.union_all(q2).all() 不會(huì)去重

?多對(duì)多的操作：

多對(duì)多連表操作

需求以及數(shù)據(jù)庫(kù)結(jié)構(gòu)

需求:

三張表:

主機(jī)表:包括nid hostname port ip

管理員表:包括:nid username

主機(jī)對(duì)應(yīng)管理員表: nid 主機(jī)id,管理員id

一個(gè)管理員帳號(hào)(比如root),可以關(guān)聯(lián)多臺(tái)服務(wù)器,一個(gè)服務(wù)器也可以有多個(gè)管理員帳號(hào)

先來(lái)看下數(shù)據(jù)結(jié)構(gòu)吧:

from sqlalchemy import create_engine from sqlalchemy.ext.declarative import declarative_base from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index from sqlalchemy.orm import sessionmaker, relationship engine = create_engine("mysql+pymysql://root:7ujm8ik,@192.168.4.193:3306/testsql?charset=utf8", max_overflow=5) Base = declarative_base() #多對(duì)多 class HostToHostUser(Base): __tablename__ = 'host_to_host_user' id = Column(Integer, primary_key=True,autoincrement=True) host_id = Column(Integer,ForeignKey('host.id')) host_user_id = Column(Integer,ForeignKey('host_user.nid')) #多對(duì)多操作 host = relationship('Host',backref='h')#backref='h'表示host表自動(dòng)生成某種關(guān)聯(lián)關(guān)系，這個(gè)關(guān)系就成為‘h’關(guān)系，只要下邊某個(gè)表中的backref也指明了這個(gè)關(guān)系‘h’，那么host表就會(huì)與該表形成關(guān)聯(lián)，基于'h'關(guān)系，這是道不清理不明的一種關(guān)系 host_user = relationship('HostUser',backref='u')#backref='u'表示host_user表自動(dòng)生成某種關(guān)聯(lián)關(guān)系，只要下邊某個(gè)表中的backref也指明了這個(gè)關(guān)系‘u‘，那么host_user表就會(huì)與該表形成關(guān)聯(lián)，基于'u'關(guān)系 （如果某張表中寫了關(guān)聯(lián)關(guān)系，關(guān)系表中就可以不用寫了）
#查詢方法：host_obj = session.query(Host).filter(Host.hostname =='c1').first()
print(host_obj.host_user) class Host(Base): __tablename__ = 'host' nid = Column(Integer, primary_key=True,autoincrement=True) hostname = Column(String(32)) port = Column(String(32)) ip = Column(String(32)) ####最簡(jiǎn)單的方式,添加此行就行（另外一種方法，可以將關(guān)系放在某張表中）: host_user=relationship('HostUser',secondary=HostToHostUser.__table__,backref='h')#這里backref指明了‘h’關(guān)系，那么host表就會(huì)與host_user表生成關(guān)聯(lián)關(guān)系 ?#格式：表名(本類是host表，這里寫要跟host關(guān)聯(lián)的表)=relationship('對(duì)象名(本類是host表，這里寫要跟host關(guān)聯(lián)的表的對(duì)象名)',?secondary=中間表的對(duì)象名, backref=關(guān)聯(lián)關(guān)系'h') class HostUser(Base): __tablename__ = 'host_user' nid = Column(Integer, primary_key=True,autoincrement=True) username = Column(String(32)) def init_db(): Base.metadata.create_all(engine) # init_db() def drop_db(): Base.metadata.drop_all(engine) Session = sessionmaker(bind=engine) session = Session() #======多對(duì)多操作 # session.add_all([ # Host(hostname='c1',port='22',ip='1.1.1.1'), # Host(hostname='c2',port='22',ip='1.1.1.2'), # Host(hostname='c3',port='22',ip='1.1.1.3'), # Host(hostname='c4',port='22',ip='1.1.1.4'), # Host(hostname='c5',port='22',ip='1.1.1.5'), # ]) # session.commit() # session.add_all([ # HostUser(username='root'), # HostUser(username='db'), # HostUser(username='nb'), # HostUser(username='sb'), # ]) # session.commit() # session.add_all([ # HostToHostUser(host_id=1,host_user_id=1), # HostToHostUser(host_id=1,host_user_id=2), # HostToHostUser(host_id=1,host_user_id=3), # HostToHostUser(host_id=2,host_user_id=2), # HostToHostUser(host_id=2,host_user_id=4), # HostToHostUser(host_id=2,host_user_id=3), # ]) # session.commit()

虛擬關(guān)系的查詢

需求:查詢主機(jī)C1的管理員帳號(hào)

# 1.反向查找,查詢host表中c1的信息,會(huì)得到一個(gè)對(duì)象,對(duì)象中存在一個(gè)已經(jīng)設(shè)置好的虛擬關(guān)系:h host_obj = session.query(Host).filter(Host.hostname == 'c1').first() #2.正向查找,遍歷對(duì)象屬性 for item in host_obj.h: print(item.host_user.username)

(整個(gè)過(guò)程經(jīng)歷了一個(gè)循環(huán)，通過(guò)host找到hosttouser，在通過(guò)hosttouser中的backref的h，列出所有與c1有關(guān)的數(shù)據(jù))

結(jié)果:

root db nb

注意:多對(duì)多的話,正反查詢都是遍歷對(duì)象中的屬性

同一需求最簡(jiǎn)單的方式

需求還是同上:查詢主機(jī)C1的管理員帳號(hào)

需要在兩張表的一張表中加一條host_user=relationship('HostUser',secondary=HostToHostUser.__table__,backref='h'),我加到了host表中

#最簡(jiǎn)單的查詢方式:host_obj = session.query(Host).filter(Host.hostname == 'c1').first() print(host_obj.host_user) for item in host_obj.host_user: print(item.username)

結(jié)果:

[<__main__.HostUser object at 0x103778710>, <__main__.HostUser object at 0x103778d68>, <__main__.HostUser object at 0x103778e10>] root db nb

轉(zhuǎn)載于:https://www.cnblogs.com/l-w-q/p/6265485.html

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