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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()
    View Code

    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
    View Code

    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()
    View Code

    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()
    View Code

    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'])
    View Code

    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()
    表结构加数据库连接
    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()
    增
    1 session.query(Users).filter(Users.id > 2).delete()
2 session.commit()
    删
    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()
    改
    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()
    查
     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()
    其他
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  • 原文地址：https://www.cnblogs.com/kading/p/6090762.html
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