Django项目配置多个数据库

给一个项目配置多个数据库，不同app里的model对应不同的数据库

settings中的设置

# 设置3个数据库

DATABASES = {
    'users_base': {
        'ENGINE': 'django.db.backends.mysql',
        "HOST": "127.0.0.1",
        "NAME": "thunder_blended_learning",
        "PASSWORD": "root",
        "USER": "root",
        "PORT": 3306,
        'OPTIONS': {'charset': 'utf8mb4'},
    },
    'cms': {
        'ENGINE': 'django.db.backends.mysql',
        "HOST": "127.0.0.1",
        "NAME": "thunder_blended_learning",
        "PASSWORD": "root",
        "USER": "root",
        "PORT": 3306,
        'OPTIONS': {'charset': 'utf8mb4'},
    },
    'default': {
        'ENGINE': 'django.db.backends.mysql',
        "HOST": "127.0.0.1",
        "NAME": "xuetangx",
        "PASSWORD": "root",
        "USER": "root",
        "PORT": 3306,
        'OPTIONS': {'charset': 'utf8mb4'},
    }
}

# 不同app可能对应不同的db，注意在本站app: cms，users_base,users_up不允许被migrate
DATABASE_ROUTERS = ['new_xuetangx.app_db_router.UsersBaseDBRouter','new_xuetangx.app_db_router.CmsDBRouter']

app_db_router文件中设置不同的app对应的数据库的名字，没有指定数据库的app用默认的default数据库

class UsersBaseDBRouter(object):
    """
    A router to control all database operations on models in the
    auth application.
    """
    def db_for_read(self, model, **hints):
        """
        Attempts to read auth models go to auth_db.
        """
        if model._meta.app_label == 'users_base':
            return 'users_base'
        if model._meta.app_label == 'auth':
            return 'users_base'
        return None

    def db_for_write(self, model, **hints):
        """
        Attempts to write auth models go to auth_db.
        """
        if model._meta.app_label == 'users_base':
            return 'users_base'
        if model._meta.app_label == 'auth':
            return 'users_base'
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """
        Allow relations if a model in the auth app is involved.
        """
        if obj1._meta.app_label == 'users_base' or 
                obj2._meta.app_label == 'users_base':
            return True
        if obj1._meta.app_label == 'auth' or 
                obj2._meta.app_label == 'auth':
            return True
        return None
    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """
        do not allow migrate to users_base's db.
        """
        if db == 'users_base' or app_label == 'users_base' or app_label == 'auth':
            return False
        else:
            return None


class CmsDBRouter(object):
    """
    A router to control all database operations on models in the
    auth application.
    """
    def db_for_read(self, model, **hints):
        """
        Attempts to read auth models go to auth_db.
        """
        if model._meta.app_label == 'cms':
            return 'cms'
        return None

    def db_for_write(self, model, **hints):
        """
        Attempts to write auth models go to auth_db.
        """
        if model._meta.app_label == 'cms':
            return 'cms'
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """
        Allow relations if a model in the auth app is involved.
        """
        if obj1._meta.app_label == 'cms' or 
                obj2._meta.app_label == 'cms':
            return True
        return None
    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """
        do not allow migrate to cms's db.
        """
        if db == 'cms' or app_label == 'cms':
            return False
        else:
            return None

   上述设置表示，app：auth , users_base 使用users_base 数据库，可读可写，可以在app内进行表关联操作，不可以进行migrate操作

                        app:cms 使用cms 数据库，可读可写，可以在app内进行表关联操作，不可以进行migrate操作

                        其他的app使用default 数据库

class LmsDBRouter(object):
    """
    A router to control all database operations on models in the
    auth application.
    """
    def db_for_read(self, model, **hints):
        """
        Attempts to read auth models go to auth_db.
        """
        if model._meta.app_label == 'lms':
            return 'default'
        return None

    def db_for_write(self, model, **hints):
        """
        Attempts to write auth models go to auth_db.
        """
        if model._meta.app_label == 'lms':
            return 'default'
        return None

    def allow_relation(self, obj1, obj2, **hints):
        """
        Allow relations if a model in the auth app is involved.
        """
        if obj1._meta.app_label == 'lms' or 
                obj2._meta.app_label == 'lms':
            return True
        return None
    def allow_migrate(self, db, app_label, model_name=None, **hints):
        """
        can only migrate lms app. Other app are not allowed to be migrated here
        """
        if app_label == 'lms':
            return db == 'default'
        return False

上述设置表示，app：lms 使用 default 数据库，可读可写，可以在app内进行表关联操作，可以进行migrate操作

另外若不写上述lms的配置，也能起到相应的作用，再次写出仅供学习之用

参考官网：https://docs.djangoproject.com/en/2.1/topics/db/multi-db/