是否可以在 sqlalchemy 中同时使主键和外键唯一

Question

I have my table like this and I want siteid and device as unique and also there must be a primary key to this table. So I assigned device as primary key.

class SiteRoleMapping(db.Model):
    __table_name__ = "site_role_mapping"
    siteid = Column(ForeignKey(('cmp_site.id'), ondelete='CASCADE'), nullable=False)
    device = Column(String, primary_key=True)
    rolename = Column(String)
    description = Column(String, default="None")

Answer 1

Without knowing much about your database, I think you should just give the mapping an Integer Primary Key and add a unique constraint on the two fields you want to have unique.

Like this:

from sqlalchemy import UniqueConstraint

class SiteRoleMapping(db.Model):
    __table_name__ = "site_role_mapping"
    id = Column(Integer, primary_key)
    site_id = Column(ForeignKey('cmp_site.id', ondelete='CASCADE'), nullable=False)
    device = Column(String, primary_key=True)
    rolename = Column(String)
    description = Column(String, default="None")

    # add unique constraint
    __table_args__ = (UniqueConstraint('site_id', 'device'), )

However, reading the table name mapping, it sounds like you are implementing a many-to-many relationship between sites and roles. This is usually done using three tables, one for sites, one for roles and one for the mapping

So I would expect a mapping to have two foreign keys, not just one.