How to use thinkorm to implement related queries between data tables

How to use thinkorm to implement associated queries between data tables

Introduction:
During database development, we often encounter situations where we need to perform associated queries between multiple data tables. Using thinkorm, an excellent database ORM framework, you can easily implement associated queries of data tables and improve development efficiency. This article will introduce how to use thinkorm to implement related queries between data tables, and provide code examples to help readers better understand.

1. Basic concepts
Before performing associated queries, you first need to understand several basic concepts in thinkorm:

1. Model: The model in thinkorm is a Class used to represent a data table.
2. Relation: Relation refers to the connection relationship between one model and another model.
3. Relation Type: Depending on the connection relationship, relationships can be divided into one-to-one (hasOne), one-to-many (hasMany), many-to-many (belongsToMany) and other types.

2. One-to-one correlation query
One-to-one correlation query refers to the correlation between one model and another model through foreign keys. The following is a sample code for using thinkorm to perform a one-to-one association query:

# 导入必要的模块
from thinkorm import Model, database

# 创建数据库实例
db = database()

# 定义模型
class User(Model):
    __table__ = 'users'
    __primary_key__ = 'id'

class UserProfile(Model):
    __table__ = 'user_profiles'
    __primary_key__ = 'id'

# 创建关联关系
User.hasOne({'profile': {'model': UserProfile, 'foreign_key': 'user_id'}})
UserProfile.belongsTo({'user': {'model': User, 'foreign_key': 'user_id'}})

# 查询
user = User.get(1)
profile = user.profile

print(user.name)        # 输出用户姓名
print(profile.bio)      # 输出用户简介

In the above sample code, a one-to-one association relationship is created by using the hasOne and belongsTo methods on the User model and UserProfile model. Among them, the parameter model represents the associated model, and foreign_key represents the foreign key field.

3. One-to-many association query
One-to-many association query refers to the association between one model and another model through foreign keys, and one model corresponds to multiple other models. The following is a sample code for using thinkorm to perform a one-to-many association query:

# 导入必要的模块
from thinkorm import Model, database

# 创建数据库实例
db = database()

# 定义模型
class User(Model):
    __table__ = 'users'
    __primary_key__ = 'id'

class Post(Model):
    __table__ = 'posts'
    __primary_key__ = 'id'

# 创建关联关系
User.hasMany({'posts': {'model': Post, 'foreign_key': 'user_id'}})
Post.belongsTo({'user': {'model': User, 'foreign_key': 'user_id'}})

# 查询
user = User.get(1)
posts = user.posts

for post in posts:
    print(post.title)   # 输出文章标题

In the above sample code, a one-to-many association relationship is created by using the hasMany and belongsTo methods on the User model and Post model. All articles published by this user can be obtained through user.posts.

4. Many-to-many correlation query
Many-to-many correlation query refers to the correlation between one model and another model through an intermediate table, and one model can correspond to multiple other models. The following is a sample code for using thinkorm to perform a many-to-many association query:

# 导入必要的模块
from thinkorm import Model, database

# 创建数据库实例
db = database()

# 定义模型
class User(Model):
    __table__ = 'users'
    __primary_key__ = 'id'

class Role(Model):
    __table__ = 'roles'
    __primary_key__ = 'id'
    
Role.belongsToMany({'users': {'model': User, 'through': 'user_roles', 'foreignKey': 'role_id', 'otherKey': 'user_id'}})
User.belongsToMany({'roles': {'model': Role, 'through': 'user_roles', 'foreignKey': 'user_id', 'otherKey': 'role_id'}})

# 查询
user = User.get(1)
roles = user.roles

for role in roles:
    print(role.name)   # 输出角色名称

In the above sample code, a many-to-many association relationship is created by using the belongsToMany method on the User model and Role model. The roles owned by the user can be obtained through user.roles.

Conclusion:
Using thinkorm to implement associated queries between data tables can enable more efficient database development. This article introduces the implementation methods of one-to-one, one-to-many, and many-to-many related queries through specific sample codes, and explains the differences between related types. Readers can flexibly use these methods to improve development efficiency according to their own needs and actual conditions.

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