Python操作MySQL
本篇对于Python操作MySQL主要使用两种方式:
- 原生模块 pymysql
- ORM框架 SQLAchemy
pymysql
pymysql是Python中操作MySQL的模块,其使用方法和MySQLdb几乎相同,但Python3不支持MySQLdb。
下载安装
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pip3 install pymysql |
Python2默认无pip命令 Python3默认自带pip3命令,若终端命令执行出错,执行python3 -m pip install --upgrade pip
使用操作
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import pymysql username = input('请输入用户名:') pwd = input('请输入密码:') # 建立连接 conn = pymysql.connect( host='localhost', user='root', password="", database='db13', port=3306, charset='utf8' ) # 创建游标 cur = conn.cursor() sql = 'select * from userinfo where name="%s" and pwd="%s"'%(username,pwd) print(sql) res = cur.execute(sql) print(res) # 游标关闭 连接关闭 cur.close() conn.close() if res: print('登录成功') else : print('登录失败')
不能用字符串拼接,会被sql注入,一定不要用字符串拼接,要用参数传递
利用sql的注释来注入(--空格)
例:
import pymysql
username = input('请输入用户名:')
pwd = input('请输入密码:')
conn = pymysql.connect(
host='localhost',
user='root',
password="",
database='db13',
port=3306,
charset='utf8'
)
cur = conn.cursor()
sql = 'select * from userinfo where name="%s" and pwd="%s"'%(username,pwd)
print(sql)
res = cur.execute(sql)
print(res)
cur.close()
conn.close()
if res: print('登录成功')
else : print('登录失败')
#数据库中为 alex 123
上例中,若用户输入的username为alexsb" or 1=1 -- asdf会将-- 后的东西全注释掉,则不需要密码甚至用户名错误也可登录成功或拿到数据,即使alexsb不是alex,也会由于or 1=1成立而登录成功
1、执行SQL(增删改一定要有conn.commit())
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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
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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
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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:
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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()
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1 作业: 2 参考表结构: 3 用户类型 4 5 用户信息 6 7 权限 8 9 用户类型&权限 10 功能: 11 12 # 登陆、注册、找回密码 13 # 用户管理 14 # 用户类型 15 # 权限管理 16 # 分配权限 17 18 特别的:程序仅一个可执行文件
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。
安装:
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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:
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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。
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1 #!/usr/bin/env python 2 # -*- coding:utf-8 -*- 3 from sqlalchemy import create_engine 4 5 6 engine = create_engine("mysql+pymysql://root:123@127.0.0.1:3306/t1", max_overflow=5) 7 8 # 执行SQL 9 # cur = engine.execute( 10 # "INSERT INTO hosts (host, color_id) VALUES ('1.1.1.22', 3)" 11 # ) 12 13 # 新插入行自增ID 14 # cur.lastrowid 15 16 # 执行SQL 17 # cur = engine.execute( 18 # "INSERT INTO hosts (host, color_id) VALUES(%s, %s)",[('1.1.1.22', 3),('1.1.1.221', 3),] 19 # ) 20 21 22 # 执行SQL 23 # cur = engine.execute( 24 # "INSERT INTO hosts (host, color_id) VALUES (%(host)s, %(color_id)s)", 25 # host='1.1.1.99', color_id=3 26 # ) 27 28 # 执行SQL 29 # cur = engine.execute('select * from hosts') 30 # 获取第一行数据 31 # cur.fetchone() 32 # 获取第n行数据 33 # cur.fetchmany(3) 34 # 获取所有数据 35 # 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
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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)
注:设置外检的另一种方式 ForeignKeyConstraint(['other_id'], ['othertable.other_id'])
2、操作表
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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()
- 增
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()
- 删
session.query(Users).filter(Users.id > 2).delete() session.commit()
- 改
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()
- 查
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() 5 6 ret = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(User.id).all() 7 8 ret = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()
- 其他
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()
更多功能参见文档,猛击这里下载PDF
DBUtils - Python数据库连接池
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import pymysql from DBUtils.PooledDB import PooledDB POOL = PooledDB( creator=pymysql, # 使用链接数据库的模块 maxconnections=6, # 连接池允许的最大连接数,0和None表示不限制连接数 mincached=2, # 初始化时,链接池中至少创建的空闲的链接,0表示不创建 maxcached=5, # 链接池中最多闲置的链接,0和None不限制 maxshared=3, # 链接池中最多共享的链接数量,0和None表示全部共享。PS: 无用,因为pymysql和MySQLdb等模块的 threadsafety都为1,所有值无论设置为多少,_maxcached永远为0,所以永远是所有链接都共享。 blocking=True, # 连接池中如果没有可用连接后,是否阻塞等待。True,等待;False,不等待然后报错 maxusage=None, # 一个链接最多被重复使用的次数,None表示无限制 setsession=[], # 开始会话前执行的命令列表。如:["set datestyle to ...", "set time zone ..."] ping=0, # ping MySQL服务端,检查是否服务可用。 # 如:0 = None = never, # 1 = default = whenever it is requested, # 2 = when a cursor is created, # 4 = when a query is executed, # 7 = always host="127.0.0.1", port=3306, user="root", password="", charset="utf8", db="day115" ) conn = POOL.connection() # pymysql - conn cur = conn.cursor(cursor=pymysql.cursors.DictCursor) sql = "select * from users WHERE name='jwb' and age=73 " res = cur.execute(sql) print(cur.fetchall()) conn.close()
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import pymysql from DBUtils.PooledDB import PooledDB POOL = PooledDB( creator=pymysql, # 使用链接数据库的模块 maxconnections=6, # 连接池允许的最大连接数,0和None表示不限制连接数 mincached=2, # 初始化时,链接池中至少创建的空闲的链接,0表示不创建 maxcached=5, # 链接池中最多闲置的链接,0和None不限制 maxshared=3, # 链接池中最多共享的链接数量,0和None表示全部共享。PS: 无用,因为pymysql和MySQLdb等模块的 threadsafety都为1,所有值无论设置为多少,_maxcached永远为0,所以永远是所有链接都共享。 blocking=True, # 连接池中如果没有可用连接后,是否阻塞等待。True,等待;False,不等待然后报错 maxusage=None, # 一个链接最多被重复使用的次数,None表示无限制 setsession=[], # 开始会话前执行的命令列表。如:["set datestyle to ...", "set time zone ..."] ping=0, # ping MySQL服务端,检查是否服务可用。 # 如:0 = None = never, # 1 = default = whenever it is requested, # 2 = when a cursor is created, # 4 = when a query is executed, # 7 = always host="127.0.0.1", port=3306, user="root", password="", charset="utf8", db="day115" ) def create_conn(): conn = POOL.connection() cursor = conn.cursor(cursor=pymysql.cursors.DictCursor) return conn,cursor def close_conn(conn,cursor): cursor.close() conn.close() def insert(sql,args): conn,cursor = create_conn() res = cursor.execute(sql,args) conn.commit() close_conn(conn,cursor) return res def fetch_one(sql,args): conn,cursor = create_conn() cursor.execute(sql,args) res = cursor.fetchone() close_conn(conn,cursor) return res def fetch_all(sql,args): conn,cursor = create_conn() cursor.execute(sql,args) res = cursor.fetchall() close_conn(conn,cursor) return res # sql = "insert into users(name,age) VALUES (%s, %s)" # insert(sql,("mjj",9)) sql = "select * from users where name=%s and age=%s" print(fetch_one(sql,("mjj",9)))
pip install DBUtils
创建数据库连接池:
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import time import pymysql import threading from DBUtils.PooledDB import PooledDB, SharedDBConnection POOL = PooledDB( creator=pymysql, # 使用链接数据库的模块 maxconnections=6, # 连接池允许的最大连接数,0和None表示不限制连接数 mincached=2, # 初始化时,链接池中至少创建的空闲的链接,0表示不创建 maxcached=5, # 链接池中最多闲置的链接,0和None不限制 maxshared=3, # 链接池中最多共享的链接数量,0和None表示全部共享。PS: 无用,因为pymysql和MySQLdb等模块的 threadsafety都为1,所有值无论设置为多少,_maxcached永远为0,所以永远是所有链接都共享。 blocking=True, # 连接池中如果没有可用连接后,是否阻塞等待。True,等待;False,不等待然后报错 maxusage=None, # 一个链接最多被重复使用的次数,None表示无限制 setsession=[], # 开始会话前执行的命令列表。如:["set datestyle to ...", "set time zone ..."] ping=0, # ping MySQL服务端,检查是否服务可用。# 如:0 = None = never, 1 = default = whenever it is requested, 2 = when a cursor is created, 4 = when a query is executed, 7 = always host='127.0.0.1', port=3306, user='root', password='123', database='pooldb', charset='utf8' )
使用数据库连接池:
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def func(): # 检测当前正在运行连接数的是否小于最大链接数,如果不小于则:等待或报raise TooManyConnections异常 # 否则 # 则优先去初始化时创建的链接中获取链接 SteadyDBConnection。 # 然后将SteadyDBConnection对象封装到PooledDedicatedDBConnection中并返回。 # 如果最开始创建的链接没有链接,则去创建一个SteadyDBConnection对象,再封装到PooledDedicatedDBConnection中并返回。 # 一旦关闭链接后,连接就返回到连接池让后续线程继续使用。 conn = POOL.connection() cursor = conn.cursor() cursor.execute('select * from tb1') result = cursor.fetchall() conn.close()
自制sqlhelper
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class MySQLhelper(object): def __init__(self, host, port, dbuser, password, database): self.pool = PooledDB( creator=pymysql, # 使用链接数据库的模块 maxconnections=6, # 连接池允许的最大连接数,0和None表示不限制连接数 mincached=2, # 初始化时,链接池中至少创建的空闲的链接,0表示不创建 maxcached=5, # 链接池中最多闲置的链接,0和None不限制 maxshared=3, # 链接池中最多共享的链接数量,0和None表示全部共享。PS: 无用,因为pymysql和MySQLdb等模块的 threadsafety都为1,所有值无论设置为多少,_maxcached永远为0,所以永远是所有链接都共享。 blocking=True, # 连接池中如果没有可用连接后,是否阻塞等待。True,等待;False,不等待然后报错 maxusage=None, # 一个链接最多被重复使用的次数,None表示无限制 setsession=[], # 开始会话前执行的命令列表。如:["set datestyle to ...", "set time zone ..."] ping=0, # ping MySQL服务端,检查是否服务可用。# 如:0 = None = never, 1 = default = whenever it is requested, 2 = when a cursor is created, 4 = when a query is executed, 7 = always host=host, port=int(port), user=dbuser, password=password, database=database, charset='utf8' ) def create_conn_cursor(self): conn = self.pool.connection() cursor = conn.cursor(pymysql.cursors.DictCursor) return conn,cursor def fetch_all(self, sql, args): conn,cursor = self.create_conn_cursor() cursor.execute(sql,args) result = cursor.fetchall() cursor.close() conn.close() return result def insert_one(self,sql,args): conn,cursor = self.create_conn_cursor() res = cursor.execute(sql,args) conn.commit() print(res) conn.close() return res def update(self,sql,args): conn,cursor = self.create_conn_cursor() res = cursor.execute(sql,args) conn.commit() print(res) conn.close() return res sqlhelper = MySQLhelper("127.0.0.1", 3306, "root", "1233121234567", "dragon") # sqlhelper.fetch_all("select * from user where id=%s",(1)) # sqlhelper.insert_one("insert into user VALUES (%s,%s)",("jinwangba",4)) # sqlhelper.update("update user SET name=%s WHERE id=%s",("yinwangba",1))