本文针对Python操作Mysql的两种方式
- 原生模块
- ORM框架 SQLAchemy
Pymsql
pymsql是Python中操作MySQL的模块，其使用方法和MySQLdb几乎相同。
下载安装
pip3 install pymysql
使用操作
1、执行sql语句
import pymysql
# 创建连接
# host mysql所在的IP地址
# user password 用户名、密码
# database 操作的数据库
conn = pymysql.connect(host = "114.116.51.xxx", user='root', password='root123', database='DB_Rainy')
# 创建游标
cursor = conn.cursor()
# 执行SQL，并返回收影响行数
effect_row = cursor.execute("update hosts set host = '1.1.1.2'")
# 执行SQL，并返回受影响行数
effect_row = cursor.execute("update hosts set host = '1.1.1.2' where nid > %s", (1,))
# 执行SQL，并返回受影响行数
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，不然无法保存新建或者修改的数据
# 查询不需要commeit，修改、插入、删除都需要commit
conn.commit()
# 关闭游标
cursor.close()
# 关闭连接
conn.close()
2、获取新创建数据自增ID
import pymysql
conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='root123', 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()
# 获取最新自增ID
new_id = cursor.lastrowid
3、获取查询数据
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()
# 获取最新自增ID
new_id = cursor.lastrowid
注意：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:
import pymysql
conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')
# 游标设置为字典类型
cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)
r = cursor.execute("call p1()")
result = cursor.fetchone()
conn.commit()
cursor.close()
conn.close()
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
image.png
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://:@[:]/
# pymysql
mysql+pymysql://:@/[?]
# MySQL-Connector
mysql+mysqlconnector://:@[:]/
# 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
1、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。
from sqlalchemy import create_engine
engine = create_engine("mysql+pymysql://root:[email protected]: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()
2、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。
2.1 创建表
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_engine
engine = create_engine("mysql+pymysql://root:[email protected]: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)
创建外键的另外一种方式
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:[email protected]:3306/db1",max_overflow=5)
Base = declarative_base()
class User(Base):
__tablename__ = 'userinfo'
id = Column(Integer,autoincrement=True,primary_key=True)
name = Column(String(20))
email = Column(String(32))
num = Column(Interger)
__table_args__ = (
UniqueConstraint("name",name='uix_n'),
Index('Ix_e','email')
)
class passwd(Base):
__tablename__ = 'password'
id = Column(Integer,autoincrement=True,primary_key=True)
pwd = Column(String(32))
userid = Column(Integer,ForeignKey('userinfo.id'),default='123')
def init_db():
Base.metadata.create_all(engine)
def drop_db():
Base.metadata.drop_all(engine)
2.2 操作表
增删改查
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:[email protected]:3306/db1",max_overflow=5)
Session = sessionmaker(bind=engine)
session = Session()
# 增加数据
"""
# 插入一行数据
obj = User(name='Wang',email='[email protected]')
session.add(obj)
session.commit()
session.close()
# 插入多行数据
objs = [
User(name="Rainy1",email="[email protected]"),
User(name="Rainy2",email="[email protected]"),
User(name="Rainy3",email="[email protected]"),
]
session.add_all(objs)
session.commit()
session.close()
"""
# 查询
'''
# 查询全部数据
userinfo = session.query(User).all()
for i in userinfo:
print(i.id,i.name,i.email)
# 按条件查询
userinfo = session.query(User).filter(User.name == 'Rainy')
for i in userinfo:
print(i.id,i.name,i.email)
# 查询指定列
userinfo = session.query(User.name,User.email).filter(User.name == 'Wang')
for i in userinfo:
print(i.name,i.email)
'''
# 删除
'''
# 删除指定行<先查询出来后直接删除>
info = session.query(User).filter(User.name == 'Wang').delete()
session.commit()
session.close()
# 删除全部数据
查询出全部数据后后面直接delete()
'''
# 修改
'''
# 修改指定行数据的指定列修改为指定值
info = session.query(User).filter(User.name == "Wang").update({'email':'[email protected]'})
session.commit()
session.close()
# 对指定行的指定列 拼接字符串
info = session.query(User).filter(User.id < 6).update({User.name:User.name + 'Wang'},synchronize_session=False)
session.commit()
session.close()
# 对指定行对指定列中的数字进行处理
info = session.query(User).filter(User.id < 3).update({'num': User.num + 1},synchronize_session="evaluate")
session.commit()
session.close()
'''
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 func
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()
# 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()