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python操作SQL
pymysql
pymsql是Python中操作MySQL的模块，其使用方法和MySQLdb几乎相同
一、下载安装
pip3 install pymysql
二、操作使用
1、执行SQL
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import pymysql 4 5 # 创建连接 6 conn = pymysql.connect(host=‘127.0.0.1‘, port=3306, user=‘root‘, passwd=‘123‘, db=‘t1‘) 7 # 创建游标 8 cursor = conn.cursor() 9 10 # 执行SQL，并返回收影响行数 11 effect_row = cursor.execute("update hosts set host = ‘1.1.1.2‘") 12 13 # 执行SQL，并返回受影响行数 14 #effect_row = cursor.execute("update hosts set host = ‘1.1.1.2‘ where nid > %s", (1,)) 15 16 # 执行SQL，并返回受影响行数 17 #effect_row = cursor.executemany("insert into hosts(host,color_id)values(%s,%s)", [("1.1.1.11",1),("1.1.1.11",2)]) 18 19 20 # 提交，不然无法保存新建或者修改的数据 21 conn.commit() 22 23 # 关闭游标 24 cursor.close() 25 # 关闭连接 26 conn.close()
2、获取新创建数据自增ID
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import pymysql 4 5 conn = pymysql.connect(host=‘127.0.0.1‘, port=3306, user=‘root‘, passwd=‘123‘, db=‘t1‘) 6 cursor = conn.cursor() 7 cursor.executemany("insert into hosts(host,color_id)values(%s,%s)", [("1.1.1.11",1),("1.1.1.11",2)]) 8 conn.commit() 9 cursor.close() 10 conn.close() 11 12 # 获取最新自增ID 13 new_id = cursor.lastrowid
3、获取查询数据
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import pymysql 4 5 conn = pymysql.connect(host=‘127.0.0.1‘, port=3306, user=‘root‘, passwd=‘123‘, db=‘t1‘) 6 cursor = conn.cursor() 7 cursor.execute("select * from hosts") 8 9 # 获取第一行数据 10 row_1 = cursor.fetchone() 11 12 # 获取前n行数据 13 # row_2 = cursor.fetchmany(3) 14 # 获取所有数据 15 # row_3 = cursor.fetchall() 16 17 conn.commit() 18 cursor.close() 19 conn.close()
注：在fetch数据时按照顺序进行，可以使用cursor.scroll(num,mode)来移动游标位置，如：
- cursor.scroll(1,mode=‘relative‘) # 相对当前位置移动
- cursor.scroll(2,mode=‘absolute‘) # 相对绝对位置移动
4、fetch数据类型关于默认获取的数据是元祖类型，如果想要或者字典类型的数据，即：
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 import pymysql 4 5 conn = pymysql.connect(host=‘127.0.0.1‘, port=3306, user=‘root‘, passwd=‘123‘, db=‘t1‘) 6 7 # 游标设置为字典类型 8 cursor = conn.cursor(cursor=pymysql.cursors.DictCursor) 9 r = cursor.execute("call p1()") 10 11 result = cursor.fetchone() 12 13 conn.commit() 14 cursor.close() 15 conn.close()
SQLAlchemy
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。
安装：
pip3 install SQLAlchemy
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：
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
一、内部处理
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。
#!/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
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 from sqlalchemy.ext.declarative import declarative_base 4 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index 5 from sqlalchemy.orm import sessionmaker, relationship 6 from sqlalchemy import create_engine 7 8 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5) 9 10 Base = declarative_base() 11 12 # 创建单表 13 class Users(Base): 14 __tablename__ = ‘users‘ 15 id = Column(Integer, primary_key=True) 16 name = Column(String(32)) 17 extra = Column(String(16)) 18 19 __table_args__ = ( 20 UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘), 21 Index(‘ix_id_name‘, ‘name‘, ‘extra‘), 22 ) 23 24 25 # 一对多 26 class Favor(Base): 27 __tablename__ = ‘favor‘ 28 nid = Column(Integer, primary_key=True) 29 caption = Column(String(50), default=‘red‘, unique=True) 30 31 32 class Person(Base): 33 __tablename__ = ‘person‘ 34 nid = Column(Integer, primary_key=True) 35 name = Column(String(32), index=True, nullable=True) 36 favor_id = Column(Integer, ForeignKey("favor.nid")) 37 38 39 # 多对多 40 class Group(Base): 41 __tablename__ = ‘group‘ 42 id = Column(Integer, primary_key=True) 43 name = Column(String(64), unique=True, nullable=False) 44 port = Column(Integer, default=22) 45 46 47 class Server(Base): 48 __tablename__ = ‘server‘ 49 50 id = Column(Integer, primary_key=True, autoincrement=True) 51 hostname = Column(String(64), unique=True, nullable=False) 52 53 54 class ServerToGroup(Base): 55 __tablename__ = ‘servertogroup‘ 56 nid = Column(Integer, primary_key=True, autoincrement=True) 57 server_id = Column(Integer, ForeignKey(‘server.id‘)) 58 group_id = Column(Integer, ForeignKey(‘group.id‘)) 59 60 61 def init_db(): 62 Base.metadata.create_all(engine) 63 64 65 def drop_db(): 66 Base.metadata.drop_all(engine) 67 注：设置外检的另一种方式 ForeignKeyConstraint([‘other_id‘], [‘othertable.other_id‘])
2、操作表
1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 from sqlalchemy.ext.declarative import declarative_base 4 from sqlalchemy import Column, Integer, String, ForeignKey, UniqueConstraint, Index 5 from sqlalchemy.orm import sessionmaker, relationship 6 from sqlalchemy import create_engine 7 8 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5) 9 10 Base = declarative_base() 11 12 # 创建单表 13 class Users(Base): 14 __tablename__ = ‘users‘ 15 id = Column(Integer, primary_key=True) 16 name = Column(String(32)) 17 extra = Column(String(16)) 18 19 __table_args__ = ( 20 UniqueConstraint(‘id‘, ‘name‘, name=‘uix_id_name‘), 21 Index(‘ix_id_name‘, ‘name‘, ‘extra‘), 22 ) 23 24 def __repr__(self): 25 return "%s-%s" %(self.id, self.name) 26 27 # 一对多 28 class Favor(Base): 29 __tablename__ = ‘favor‘ 30 nid = Column(Integer, primary_key=True) 31 caption = Column(String(50), default=‘red‘, unique=True) 32 33 def __repr__(self): 34 return "%s-%s" %(self.nid, self.caption) 35 36 class Person(Base): 37 __tablename__ = ‘person‘ 38 nid = Column(Integer, primary_key=True) 39 name = Column(String(32), index=True, nullable=True) 40 favor_id = Column(Integer, ForeignKey("favor.nid")) 41 # 与生成表结构无关，仅用于查询方便 42 favor = relationship("Favor", backref=‘pers‘) 43 44 # 多对多 45 class ServerToGroup(Base): 46 __tablename__ = ‘servertogroup‘ 47 nid = Column(Integer, primary_key=True, autoincrement=True) 48 server_id = Column(Integer, ForeignKey(‘server.id‘)) 49 group_id = Column(Integer, ForeignKey(‘group.id‘)) 50 group = relationship("Group", backref=‘s2g‘) 51 server = relationship("Server", backref=‘s2g‘) 52 53 class Group(Base): 54 __tablename__ = ‘group‘ 55 id = Column(Integer, primary_key=True) 56 name = Column(String(64), unique=True, nullable=False) 57 port = Column(Integer, default=22) 58 # group = relationship(‘Group‘,secondary=ServerToGroup,backref=‘host_list‘) 59 60 61 class Server(Base): 62 __tablename__ = ‘server‘ 63 64 id = Column(Integer, primary_key=True, autoincrement=True) 65 hostname = Column(String(64), unique=True, nullable=False) 66 67 68 69 70 def init_db(): 71 Base.metadata.create_all(engine) 72 73 74 def drop_db(): 75 Base.metadata.drop_all(engine) 76 77 78 Session = sessionmaker(bind=engine) 79 session = Session()
1 obj = Users(name="alex0", extra=‘sb‘) 2 session.add(obj) 3 session.add_all([ 4 Users(name="alex1", extra=‘sb‘), 5 Users(name="alex2", extra=‘sb‘), 6 ]) 7 session.commit()
1 session.query(Users).filter(Users.id > 2).delete() 2 session.commit()
1 session.query(Users).filter(Users.id > 2).update({"name" : "099"}) 2 session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + "099"}, synchronize_session=False) 3 session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate") 4 session.commit()
1 ret = session.query(Users).all() 2 ret = session.query(Users.name, Users.extra).all() 3 ret = session.query(Users).filter_by(name=‘alex‘).all() 4 ret = session.query(Users).filter_by(name=‘alex‘).first()
1 # 条件 2 ret = session.query(Users).filter_by(name=‘alex‘).all() 3 ret = session.query(Users).filter(Users.id > 1, Users.name == ‘eric‘).all() 4 ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == ‘eric‘).all() 5 ret = session.query(Users).filter(Users.id.in_([1,3,4])).all() 6 ret = session.query(Users).filter(~Users.id.in_([1,3,4])).all() 7 ret = session.query(Users).filter(Users.id.in_(session.query(Users.id).filter_by(name=‘eric‘))).all() 8 from sqlalchemy import and_, or_ 9 ret = session.query(Users).filter(and_(Users.id > 3, Users.name == ‘eric‘)).all() 10 ret = session.query(Users).filter(or_(Users.id < 2, Users.name == ‘eric‘)).all() 11 ret = session.query(Users).filter( 12 or_( 13 Users.id < 2, 14 and_(Users.name == ‘eric‘, Users.id > 3), 15 Users.extra != "" 16 )).all() 17 18 19 # 通配符 20 ret = session.query(Users).filter(Users.name.like(‘e%‘)).all() 21 ret = session.query(Users).filter(~Users.name.like(‘e%‘)).all() 22 23 # 限制 24 ret = session.query(Users)[1:2] 25 26 # 排序 27 ret = session.query(Users).order_by(Users.name.desc()).all() 28 ret = session.query(Users).order_by(Users.name.desc(), Users.id.asc()).all() 29 30 # 分组 31 from sqlalchemy.sql import func 32 33 ret = session.query(Users).group_by(Users.extra).all() 34 ret = session.query( 35 func.max(Users.id), 36 func.sum(Users.id), 37 func.min(Users.id)).group_by(Users.name).all() 38 39 ret = session.query( 40 func.max(Users.id), 41 func.sum(Users.id), 42 func.min(Users.id)).group_by(Users.name).having(func.min(Users.id) >2).all() 43 44 # 连表 45 46 ret = session.query(Users, Favor).filter(Users.id == Favor.nid).all() 47 48 ret = session.query(Person).join(Favor).all() 49 50 ret = session.query(Person).join(Favor, isouter=True).all() 51 52 53 # 组合 54 q1 = session.query(Users.name).filter(Users.id > 2) 55 q2 = session.query(Favor.caption).filter(Favor.nid < 2) 56 ret = q1.union(q2).all() 57 58 q1 = session.query(Users.name).filter(Users.id > 2) 59 q2 = session.query(Favor.caption).filter(Favor.nid < 2) 60 ret = q1.union_all(q2).all()
python操作SQL
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