本文針對 Python 操做 MySQL 主要使用的兩種方式講解:html
本章內容: python
pymsql 是 Python 中操做 MySQL 的原生模塊,其使用方法和 MySQL 的SQL語句幾乎相同mysql
pip3 install pymysql
執行 SQL 語句的基本語法:sql
須要注意的是:建立連接後,都由遊標來進行與數據庫的操做,固然,拿到數據也靠遊標數據庫
#!/usr/bin/env python # -*- coding:utf-8 -*- import pymysql # 建立鏈接 conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1') # 建立遊標 cursor = conn.cursor() # 執行SQL,並返回收影響行數 effect_row = cursor.execute("update hosts set host = '1.1.1.2'") # 執行SQL,並返回受影響行數 #effect_row = cursor.execute("update hosts set host = '1.1.1.2' where nid > %s", (1,)) # 執行SQL,並返回受影響行數 #effect_row = cursor.executemany("insert into hosts(host,color_id)values(%s,%s)", [("1.1.1.11",1),("1.1.1.11",2)]) # 提交,否則沒法保存新建或者修改的數據 conn.commit() # 關閉遊標 cursor.close() # 關閉鏈接 conn.close()
能夠獲取到最新自增的ID,也就是最後插入的一條數據IDsession
#!/usr/bin/env python # -*- coding:utf-8 -*- import pymysql conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1') cursor = conn.cursor() cursor.executemany("insert into hosts(host,color_id)values(%s,%s)", [("1.1.1.11",1),("1.1.1.11",2)]) conn.commit() cursor.close() conn.close() # 獲取最新自增ID new_id = cursor.lastrowid
獲取查詢數據的三種方式:oracle
#!/usr/bin/env python # -*- coding:utf-8 -*- import pymysql conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1') cursor = conn.cursor() cursor.execute("select * from hosts") # 獲取第一行數據 row_1 = cursor.fetchone() # 獲取前n行數據 # row_2 = cursor.fetchmany(3) # 獲取全部數據 # row_3 = cursor.fetchall() conn.commit() cursor.close() conn.close()
操做都是靠遊標,那對遊標的控制也是必須的框架
注:在fetch數據時按照順序進行,能夠使用cursor.scroll(num,mode)來移動遊標位置,如: cursor.scroll(1,mode='relative') # 相對當前位置移動 cursor.scroll(2,mode='absolute') # 相對絕對位置移動
默認拿到的數據是小括號,元祖類型,若是是字典的話會更方便操做,那方法來了:ide
# 關於默認獲取的數據是元祖類型,若是想要或者字典類型的數據,即: #!/usr/bin/env python # -*- coding:utf-8 -*- import pymysql conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1') # 遊標設置爲字典類型 cursor = conn.cursor(cursor=pymysql.cursors.DictCursor) r = cursor.execute("call p1()") result = cursor.fetchone() conn.commit() cursor.close() conn.close()
每次鏈接數據庫都須要鏈接和關閉,啊,好多代碼,那麼方法又來了:函數
是否是很屌啊?
# 利用with定義函數 @contextlib.contextmanager def mysql(self, host='127.0.0.1', port=3306, user='nick', passwd='', db='db1', charset='utf8'): self.conn = pymysql.connect(host=host, port=port, user=user, passwd=passwd, db=db, charset=charset) self.cuersor = self.conn.cursor(cursor=pymysql.cursors.DictCursor) try: yield self.cuersor finally: self.conn.commit() self.cuersor.close() self.conn.close() # 執行 with mysql() as cuersor: print(cuersor) # 操做MySQL代碼塊
SQLAlchemy 簡稱 ORM 框架,該框架創建在數據庫的 API 之上,使用關係對象映射來進行數據庫操做;
簡言之即是:將類對象轉換成 SQL 語句,而後使用數據 API 執行 SQL 語句並獲取執行結果。
pip3 install SQLAlchemy
須要注意了:SQLAlchemy 本身沒法操做數據庫,必須結合 pymsql 等第三方插件,Dialect 用於和數據 API 進行交互,根據配置文件的不一樣調用不一樣的數據庫 API,從而實現對數據庫的操做,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 進行數據庫操做,Engine使用ConnectionPooling鏈接數據庫,而後再經過Dialect執行SQL語句。
#!/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) # 執行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 # ) # 執行SQL # cur = engine.execute('select * from hosts') # 獲取第一行數據 # cur.fetchone() # 獲取第n行數據 # cur.fetchmany(3) # 獲取全部數據 # cur.fetchall()
使用 ORM/Schema Type/SQL Expression Language/Engine/ConnectionPooling/Dialect 全部組件對數據進行操做。
根據類建立對象,對象轉換成SQL,執行SQL。
#!/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 # 指定字符集、最大鏈接池數 engine = create_engine("mysql+pymysql://root:suoning@127.0.0.1:3306/suoning4?charset=utf8", max_overflow=5) Base = declarative_base() # 建立單表 class Users(Base): # 表名 __tablename__ = 'users' # 表字段 id = Column(Integer, primary_key=True) # 主鍵、默認自增 name = Column(String(32)) extra = Column(String(16)) __table_args__ = ( UniqueConstraint('id', 'name', name='uix_id_name'), # 惟一索引 Index('ix_id_name', 'name', 'extra'), # 普通索引 ) def __repr__(self): # 查是輸出的內容格式,本質仍是對象 return "%s-%s" %(self.id, self.name) # 一對多 class Favor(Base): __tablename__ = 'favor' nid = Column(Integer, primary_key=True) caption = Column(String(50), default='red', unique=True) # 默認值、惟一索引 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")) # 與生成表結構無關,僅用於查詢方便 favor = relationship("Favor", backref='pers') # 多對多 class ServerToGroup(Base): # 關係表要放對應表上面,不然找不到 __tablename__ = 'servertogroup' nid = Column(Integer, primary_key=True, autoincrement=True) server_id = Column(Integer, ForeignKey('server.id')) # 外鍵 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) # 不能爲空 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) # 自增 hostname = Column(String(64), unique=True, nullable=False) def init_db(): # 建立表 Base.metadata.create_all(engine) def drop_db(): # 刪除表 Base.metadata.drop_all(engine)
注:設置外檢的另外一種方式 ForeignKeyConstraint(['other_id'], ['othertable.other_id'])
操做表那必須導入模塊,建立相應類,相應增\刪\改\查的語法,詳細見下code吧^^:
#!/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 # 指定字符集、最大鏈接池數 engine = create_engine("mysql+pymysql://root:suoning@127.0.0.1:3306/suoning4?charset=utf8", max_overflow=5) Base = declarative_base() # 建立單表 class Users(Base): # 表名 __tablename__ = 'users' # 表字段 id = Column(Integer, primary_key=True) # 主鍵、默認自增 name = Column(String(32)) extra = Column(String(16)) __table_args__ = ( UniqueConstraint('id', 'name', name='uix_id_name'), # 惟一索引 Index('ix_id_name', 'name', 'extra'), # 普通索引 ) def __repr__(self): # 查是輸出的內容格式,本質仍是對象 return "%s-%s" %(self.id, self.name) # 一對多 class Favor(Base): __tablename__ = 'favor' nid = Column(Integer, primary_key=True) caption = Column(String(50), default='red', unique=True) # 默認值、惟一索引 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")) # 與生成表結構無關,僅用於查詢方便 favor = relationship("Favor", backref='pers') # 多對多 class ServerToGroup(Base): # 關係表要放對應表上面,不然找不到 __tablename__ = 'servertogroup' nid = Column(Integer, primary_key=True, autoincrement=True) server_id = Column(Integer, ForeignKey('server.id')) # 外鍵 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) # 不能爲空 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) # 自增 hostname = Column(String(64), unique=True, nullable=False) def init_db(): # 建立表 Base.metadata.create_all(engine) def drop_db(): # 刪除表 Base.metadata.drop_all(engine) # 先實例化sessionmaker類,Session對象加括號執行類下的__call__方法, # 獲得session對象,因此session能夠調用Session類下的add,add_all等方法 Session = sessionmaker(bind=engine) # 指定引擎 session = Session()
# 增 # 添加一條 obj = Users(name="張三", extra='三兒') session.add(obj) # 添加多條 session.add_all([ Users(name="李四", extra='四兒'), Users(name="汪五", extra='五兒'), ]) # 提交 session.commit()
# 刪 session.query(Users).filter(Users.id > 2).delete() session.query(Users).filter_by(id = 1).delete() session.commit()
# 改 session.query(Users).filter(Users.id > 2).update({"name" : "nick"}) session.query(Users).filter(Users.id > 2).update({"name" : "nick", "extra":"niubily"}) session.query(Users).filter(Users.id > 2).update({Users.name: Users.name + "Suo"}, synchronize_session=False) session.query(Users).filter(Users.id > 2).update({"num": Users.num + 1}, synchronize_session="evaluate") session.commit()
# 查 # all()結果爲對象列表,first()爲具體對象 ret = session.query(Users).all() ret = session.query(Users.name, Users.extra).all() ret = session.query(Users).filter_by(name='nick').all() ret = session.query(Users).filter_by(name='nick').first() print(ret)
那如何加限制條件等,我要更靈活使用,好吧,仍是見下 code:
# 條件 ret = session.query(Users).filter_by(name='nick').all() ret = session.query(Users).filter(Users.id > 1, Users.name == 'nick').all() ret = session.query(Users).filter(Users.id.between(1, 3), Users.name == 'nick').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='nick'))).all() from sqlalchemy import and_, or_ # 導入模塊 ret = session.query(Users).filter(and_(Users.id > 3, Users.name == 'nick')).all() ret = session.query(Users).filter(or_(Users.id < 2, Users.name == 'nick')).all() ret = session.query(Users).filter( or_( Users.id < 2, and_(Users.name == 'nick', Users.id > 3), Users.extra != "" )).all() # 通配符 ret = session.query(Users).filter(Users.name.like('n%')).all() ret = session.query(Users).filter(~Users.name.like('n%')).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 func # 導入模塊 ret = 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() ret = session.query(Person).join(Favor, isouter=True).all() # isouter=True 理解爲 left join ,若是不寫爲 inner join # 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() q1 = session.query(Users.name).filter(Users.id > 2) q2 = session.query(Favor.caption).filter(Favor.nid < 2) ret = q1.union_all(q2).all()