Python大神-python操作Mysql

Python操作Mysql的方式有兩種：

　　1）python的第三種模塊：pymysql

　　2）ORM框架

一、pymysql

　　1、下載安裝

　　　　pip3 install pymysql

　　2、操作方法

#!/usr/bin/env python
# -*- coding:utf-8 -*-
import pymysql
  
# 創建連接
conn = pymysql.connect(host='127.0.0.1', port=3306, user='root', passwd='123', db='t1')
# 創建游標
cursor = conn.cursor()

========sql語句的操作區間（都是把sql語句以字符串的形式來寫）=====================
  
# 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,))  # 不可用Python中的字符串替換，否則會有漏洞
  
# 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)])
  
========sql語句的操作區間=====================
  
# 提交，不然無法保存新建或者修改的數據
conn.commit()
  
# 關閉游標
cursor.close()
# 關閉連接
conn.close()

　　3、獲取新創建數據自增ID（數據庫表的最新id值）

# 獲取最新自增ID
new_id = cursor.lastrowid

　　4、獲取查詢數據--fetchone;fetchmany();fetchall

　　　　注：1）獲取查詢數據的結果為元組類型

　　　　　　2）在fetch數據時按照順序進行，可以使用cursor.scroll(num,mode)來移動游標位置，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

#!/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)
# 獲取所有數據
# row_3 = cursor.fetchall()
  
conn.commit()
cursor.close()
conn.close()

　　5、修改fetch數據類型

# 游標設置為字典類型
cursor = conn.cursor(cursor=pymysql.cursors.DictCursor)

 

二、ORM（sqlAlchemy）

　　1、准備工作

　　　　ORM是無法獨立對數據庫進行操作，需要與數據庫API

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

　　2、安裝

　　　　1)pip3 install pymysql    # 數據庫API

　　　　2) pip3 install SQLAlchemy

　　3、簡單操作數據表（onlyone）

import pymysql
from sqlalchemy import create_engine # 確定數據庫類型、數據庫與框架的接口（pymysql）、連接數據庫
from sqlalchemy.ext.declarative import declarative_base # 創建基類
from sqlalchemy import Column,Integer,String,PrimaryKeyConstraint,ForeignKey,UniqueConstraint,Index # 創建表所用的關鍵字
from sqlalchemy.orm import sessionmaker

engine = create_engine("mysql+pymysql://root@127.0.0.1:3306/day3")

# 步驟1：創建表的基類
Base = declarative_base()

# 步驟2：創建表的類
class User(Base):
    __tablename__ = "user"

    id = Column(Integer,primary_key=True)
    name = Column(String(32))
    age = Column(Integer)
    aihao = Column(String(32))

    __table_args__ = (
        # PrimaryKeyConstraint(id),
        UniqueConstraint('name',name='uq_name'),
    )

# 步驟4：新建和刪除表
# Base.metadata.drop_all(engine)
Base.metadata.create_all(engine)

# 步驟5：連接資源池-操作表
Session = sessionmaker(bind=engine)
session = Session()

# 兩種增加數據的方式
"""
u1 = User(name='sdy',age='23',aihao='paobu')
session.add(u1)
session.add_all(
    [User(name='one',age='22',aihao='ss'),
    User(name='two',age='12',aihao='dd'),]
)
"""

# 刪除-- delete()
# session.query(User).filter(User.id == 2).delete()

# 改-- update()
# session.query(User).filter_by(name='one').update({"name":"sb"})
# 注：1）filter 與 filter_by 的區別：篩選條件的寫法（filter:表名.列名 filter_by : 列名）
# 注：2）字符拼接時，要加上“synchronize_session=False”
# session.query(User).filter(User.id == 6).update({User.name: User.name + "099"}, synchronize_session=False)
# session.query(User).filter(User.id == 6).update({"age": User.age + 1}, synchronize_session="evaluate")

# 查 -- query(表名或table_name.lie_ming),all() : 把所有結果放在一個列表里 ；first() : 取第一個結果



# 只有提交后才能更改數據
session.commit()

　　4、一對多

　　注：relationship的用法

Base = declarative_base()

class Father(Base):
    __tablename__ = 'father'
    id = Column(Integer,primary_key=True)
    name = Column(String(32))
    age = Column(Integer)

class Son(Base):
    __tablename__ = 'son'
    id = Column(Integer,primary_key=True)
    name = Column(String(32))
    age = Column(Integer)
    father_id = Column(Integer,ForeignKey('father.id'))
    father = relationship('Father',backref='sons')

Base.metadata.create_all(engine)

Session = sessionmaker(bind=engine)
session = Session()

# f1 = Father(name='huang',age='40')
# f2 = Father(name='wang',age = '45')
# s1 = Son(name='xiao huang1',age='16')
# s2 = Son(name='xiao huang2',age='5')
# s3 = Son(name='xiao wang1',age='9')
#
# session.add_all([f1,f2,])
# session.commit()

# session.query(Son).filter(Son.id < 3).update({'father_id':1})
# session.query(Son).filter(Son.id > 2).update({'father_id':2})

# relationship 用法：里面封裝了join()連表查詢
ret = session.query(Son.name,Son.father_id,Son.age,Son.id).filter_by(id=2).all()

ret1 = session.query(Son).filter_by(id=2).first()
ret2 = session.query(Father).filter_by(id=1).first()
print(ret,ret1.father.name,ret2.sons)
for i in ret2.sons:
    print(i.name)


# session.add_all([s1,s2,s3,])
session.commit()

# 問題：1）給列起別名？ 2） 原來的連表查詢join的用法？

　　5、多對多

　　注：多對多時，利用relationship查詢時，建表階段relationship要加上“secondary=Women_to_Men.__table__” --- Women_to_Men 為連表關系的類名

#!/usr/bin/env python
# -*- coding:utf-8 -*-

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
import time

engine = create_engine("mysql+pymysql://root@127.0.0.1:3306/day3?charset=utf8")

Base = declarative_base()

class Women_to_Men(Base):
    __tablename__ = 'women_to_men'
    id = Column(Integer,primary_key=True)
    women_id = Column(Integer,ForeignKey('women.id'))
    men_id = Column(Integer,ForeignKey('men.id'))

class Women(Base):
    __tablename__ = 'women'
    id = Column(Integer,primary_key=True)
    name = Column(String(32))
    mens = relationship('Men',secondary=Women_to_Men.__table__,backref='womens',)

class Men(Base):
    __tablename__ = 'men'
    id = Column(Integer,primary_key=True)
    name = Column(String(32))

Base.metadata.create_all(engine)

Session = sessionmaker(bind=engine)
session = Session()

# w1 = Women(name="xiaopao")
# w2 = Women(name='xiaoji')
# m1 = Men(name='dalong')
# m2 = Men(name='dafei')
# gx = Women_to_Men(women_id = 1,men_id = 2)
# session.add_all([w1,w2,m1,m2])
# session.commit()
# session.add(gx)

women1 = session.query(Women).filter_by(id = 1).first()
print(women1,women1.mens)
mens = session.query(Men).filter_by(id = 1).first()
print(mens,mens.womens)
# women1.mens.append(mens)
session.commit()

# 總結：多對多時，利用relationship查詢時，建表階段relationship要加上“secondary=Women_to_Men.__table__” --- Women_to_Men 為連表關系的類名

　　6、查詢表的條件

ret = session.query(Users).all()
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()

ret = session.query(Users).filter(text("id<:value and name=:name")).params(value=224, name='fred').order_by(User.id).all()

ret = session.query(Users).from_statement(text("SELECT * FROM users where name=:name")).params(name='ed').all()

#　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()
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()

# 分組
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()

# 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()


# 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()