一个表中不能有两个主键。相反，您必须使用复合主键。可以通过
PrimaryKeyConstraint在模型中添加，如下所示来完成此操作（请记住在闭合括号之前，请添加逗号
__table_args__：
from db import PrimaryKeyConstraintclass EssayStateAssociations(db.Model): __tablename__ = 'essay_associations' __table_args__ = ( PrimaryKeyConstraint('application_essay_id', 'theme_essay_id'), ) application_essay_id = db.Column( db.Integer, db.ForeignKey("application_essay.id")) theme_essay_id = db.Column( db.Integer, db.ForeignKey("theme_essay.id")) state = db.Column(db.String, default="pending")
