1、先把需要做多对多的模型定义出来
2、使用Table定义一个中间表，中间表一般就是包含两个模型的外键字段就可以了，并且让他们两个来作为一个“复合主键”
3、在两个需要做多对多的模型中随便选择一个模型，定义一个relationship属性，来绑定三者之间的关系，在使用relationship的时候需要传入一个secondary中间表
1 #encoding:utf8
2 # sqlalchemy创建多对多的关系表
3 from sqlalchemy import create_engine,Column,Integer,String,Table,ForeignKey
4 from sqlalchemy.ext.declarative import declarative_base
5 from mysql_config import DB_URI
6 from sqlalchemy.orm import sessionmaker,relationship
7
8
9 # 数据库连接代码从from mysql_config import DB_URI中导入
10 # mysql连接格式
11 # DB_URI = "mysql+pymysql://{username}:{password}@{host}:{port}/{database}".format("这里填写需要的数据")
12
13 engine = create_engine(DB_URI)
14 Base = declarative_base(engine)
15 session = sessionmaker(engine)()
16
17 article_tag = Table(
18 "article_tag",
19 Base.metadata,
20 Column("article_id",Integer,ForeignKey("article.id"),primary_key=True),
21 Column("tag_id",Integer,ForeignKey("tag.id"),primary_key=True)
22 )
23 class Article(Base):
24 __tablename__ = "article"
25 id = Column(Integer,primary_key=True,autoincrement=True)
26 title = Column(String(50),nullable=False)
27 tags = relationship("Tag",backref="articles",secondary=article_tag)
28 def __repr__(self):
29 return "<Article(title:%s)>"%self.title
30 class Tag(Base):
31 __tablename__ = "tag"
32 id = Column(Integer, primary_key=True, autoincrement=True)
33 name = Column(String(50), nullable=False)
34 def __repr__(self):
35 return "<Article(name:%s)>"%self.name
36
37 def create_table():
38 Base.metadata.create_all()
39
40 #测试数据，分别给article1、article2、tag1、tag2添加两条数据
41 def add_data():
42 article1 = Article(title="article1")
43 article2 = Article(title="article2")
44 tag1 = Tag(name="tag1")
45 tag2 = Tag(name="tag2")
46
47 tag1.articles.append(article1)
48 tag1.articles.append(article2)
49
50 tag2.articles.append(article1)
51 tag2.articles.append(article2)
52 session.add(tag1)
53 session.add(tag2)
54 session.commit()
55
56 # 这是数据库插入后的数据
57 # mysql> select * from article
58 # -> ;
59 # +----+----------+
60 # | id | title |
61 # +----+----------+
62 # | 1 | article1 |
63 # | 2 | article2 |
64 # +----+----------+
65 # 2 rows in set (0.00 sec)
66 #
67 # mysql> select * from tag
68 # -> ;
69 # +----+------+
70 # | id | name |
71 # +----+------+
72 # | 1 | tag1 |
73 # | 2 | tag2 |
74 # +----+------+
75 # 2 rows in set (0.00 sec)
76 #
77 # mysql> select * from article_tag
78 # -> ;
79 # +------------+--------+
80 # | article_id | tag_id |
81 # +------------+--------+
82 # | 1 | 1 |
83 # | 2 | 1 |
84 # | 1 | 2 |
85 # | 2 | 2 |
86 # +------------+--------+
87 # 4 rows in set (0.00 sec)
88
89 #测试查询
90 def search_data():
91 article = session.query(Article).first()
92 print("这是通过article参数查找tags:%s"%article.tags)
93 tag = session.query(Tag).first()
94 print("这是通过tag参数查找article:%s"%tag.articles)
95
96 if __name__ == "__main__":
97 # create_table
98 # add_data()
99 search_data()
