django同一个项目中连接多个数据库

一、场景与思路

同一个项目中需要连接多个数据库。

二、代码

代码中主要是三个部分，settings、models以及自己写的一个类。

1.自己写的文件：database_app_router.py  类名：DatabaseAppsRouter

# database_app_router.py
# -*- coding: utf-8 -*-
from django.conf import settings

DATABASE_MAPPING = settings.DATABASES_APPS_MAPPING


class DatabaseAppsRouter(object):
    """
    A router to control all database operations on models for different
    databases.

    In case an app is not set in settings.DATABASE_APPS_MAPPING, the router
    will fallback to the `default` database.

    Settings example:

    DATABASE_APPS_MAPPING = {'app1': 'db1', 'app2': 'db2'}
    """

    def db_for_read(self, model, **hints):
        """"Point all read operations to the specific database."""
        """将所有读操作指向特定的数据库。"""
        if model._meta.app_label in DATABASE_MAPPING:
            return DATABASE_MAPPING[model._meta.app_label]
        return None

    def db_for_write(self, model, **hints):
        """Point all write operations to the specific database."""
        """将所有写操作指向特定的数据库。"""
        if model._meta.app_label in DATABASE_MAPPING:
            return DATABASE_MAPPING[model._meta.app_label]
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """Allow any relation between apps that use the same database."""
        """允许使用相同数据库的应用程序之间的任何关系"""
        db_obj1 = DATABASE_MAPPING.get(obj1._meta.app_label)
        db_obj2 = DATABASE_MAPPING.get(obj2._meta.app_label)
        if db_obj1 and db_obj2:
            if db_obj1 == db_obj2:
                return True
            else:
                return False
        else:
            return None

    def allow_syncdb(self, db, model):
        """Make sure that apps only appear in the related database."""
        """确保这些应用程序只出现在相关的数据库中。"""
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(model._meta.app_label) == db
        elif model._meta.app_label in DATABASE_MAPPING:
            return False
        return None

    def allow_migrate(self, db, app_label, model=None, **hints):
        """Make sure the auth app only appears in the 'auth_db' database."""
        """确保身份验证应用程序只出现在“authdb”数据库中。"""
        if db in DATABASE_MAPPING.values():
            return DATABASE_MAPPING.get(app_label) == db
        elif app_label in DATABASE_MAPPING:
            return False
        return None

 settings.py文件中修改

# settings.py

DATABASES = {
    "default": {
        "ENGINE": "django.db.backends.mysql",
        "NAME": "integral_wall",
        "USER": "root",
        "PASSWORD": "123456",
        "HOST": "127.0.0.1",
        "PORT": "3306",
    },
    "sdk_51zhuan": {
        "ENGINE": "django.db.backends.mysql",
        "NAME": "sdk_51zhuan",
        "USER": "root",
        "PASSWORD": "123456",
        "HOST": "127.0.0.1",
        "PORT": "3306",
    },
}

DATABASES_APPS_MAPPING = {
    'integral_wall': 'default',
    'sdk_db': 'sdk_51zhuan',
    'admin': 'sdk_51zhuan',
    'auth': 'sdk_51zhuan',

} DATABASE_ROUTERS = ['integral_wall_manager.database_app_router.DatabaseAppsRouter']

 models.py文件修改

# models.py

class SdkApplication(models.Model):
    """
    应用程序列表
    """
    sdk_type_choices = (
        (0, '不合作'),
        (1, '一定时间内合作'),
        (2, '永久合作'),
    )
    id = models.AutoField(primary_key=True)
    app_id = models.CharField('苹果商店里的APP id', max_length=16, default='')
    app_name = models.CharField('应用名称', max_length=64)
    bundle_id = models.CharField('包ID，域名倒序', max_length=64, default='')
    create_time = models.DateTimeField('创建时间', auto_now_add=True)

    class Meta:
        app_label = 'sdk_db'  # 连接的数据库
        db_table = "sdk_application"  # 表名


class AdRecord(models.Model):
    """
    广告记录
    """
    type = models.CharField('操作类型', max_length=16)
    action = models.CharField('操作、行为', max_length=16)
    create_time = models.DateTimeField('创建时间', auto_now_add=True)

    class Meta:
        # app_label 不写，使用默认
        db_table = "ad_record"  # 表名

三、执行

执行的顺序就是大家熟悉的了：

1.python manage.py makemigrations

之后的稍有不同：

2.python manage.py migrate --database=sdk_51zhuan

......

python manage.py migrate（只有默认数据库不为空时才可以这么实用，若为空则是用上面的方法）

其实在这里没有特别的执行顺序，但是我个人建议大家是最后执行migrate（即默认数据库）。另外要注意一点，admin、auth是一定要在一个app里被makemigrations放到一个XXXX_initial.py文件中的，不然你怎么migrate都不会有这些Django自建的表的！

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****最后的最后一定要注意：不在一个库里了，没法跨库建立约束关系，放弃外键，老老实实一步步查！****