python-flask sqlalchemy：如何声明基类（支持继承而不创建表的方法）

曾经终败给现在 2021-09-18 00:56 479阅读 0赞

### **如果基类没有添加属性：\_\_abstract\_\_ = True** ###

**会报如下错误：（不是基类，而是一个table，创建table要主键和关系表的外键）**

1、（没有主键）sqlalchemy.exc.ArgumentError: Mapper Mapper|Base|base could not assemble any primary key columns for mapped table 'base'

2、（没有外键）sqlalchemy.exc.NoForeignKeysError: Can't find any foreign key relationships between 'base' and 'books'.

from kirin_app.db_models import db
    
    class Base(db.Model):
        # Flask-SQLAlchemy创建table时,如何声明基类（这个类不会创建表,可以被继承）
        # 方法就是把__abstract__这个属性设置为True,这个类为基类，不会被创建为表！
        __abstract__ = True
    
        id = db.Column(db.Integer,primary_key=True)
        status = db.Column(db.Integer,default=1)

from kirin_app.db_models import db
    from kirin_app.db_models.base_model import Base
    
    class Books(Base):
        id = db.Column("id", db.Integer, primary_key=True, autoincrement=True)
        title = db.Column("title", db.String(10))
        author = db.Column("author", db.String(10))
        isbn = db.Column("isbn", db.Integer, nullable=True, unique=True)
        price = db.Column("price", db.Integer)
        binding = db.Column("binding", db.String(10))

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[sqlalchemy][]官方链接：[https://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/api.html\#abstract][sqlalchemy]

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[sqlalchemy]: https://docs.sqlalchemy.org/en/latest/orm/extensions/declarative/api.html#abstract
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