Python（Flask，SQLAlchemy）中的 InterfaceError - db.relationship 参数的错误绑定参数

Question

我对 Flask 和 SQLAlchemy 非常陌生，但对 Python 有基本的了解。这也是我在这里的第一篇文章，我想我已经广泛寻找我的问题的答案。

我正在尝试创建一个非常简单的家谱数据库。我有两个表 - 一个个人表和一个家庭表（每个家庭都有一个可选的父亲和一个可选的母亲 - 每一个都是代表个人表中另一个人的外键）。

创建个人时必须使用姓氏和可选的前名和中间名。在个人表中还有一个与族表有关系的列。

当我尝试运行此代码时，我得到一个错误 -

sqlalchemy.exc.InterfaceError: (sqlite3.InterfaceError) 绑定参数 3 错误 - 可能是不受支持的类型。 [SQL: INSERT INTO individual (forename, middle_name, surname, family_id) VALUES (?, ?, ?, ?)] [参数：('David', None, 'Bloggs', )]

代码是：

import os
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate

basedir = os.path.abspath(os.path.dirname(__file__))

app = Flask(__name__)

app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///"+os.path.join(basedir,"data.sqlite")
app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False

db = SQLAlchemy(app)
Migrate(app, db)

class Family(db.Model):

    __tablename__ = "family"

    id = db.Column(db.Integer,primary_key=True)
    mother_id = db.Column(db.Integer,db.ForeignKey("individual.id"))
    father_id = db.Column(db.Integer,db.ForeignKey("individual.id"))


    def __init__(self,mother_id='',father_id=''):
        self.mother_id = mother_id
        self.father_id = father_id


class Individual(db.Model):

    __tablename__ = "individual"

    id = db.Column(db.Integer, primary_key=True)
    forename = db.Column(db.Text)
    middle_name = db.Column(db.Text)
    surname = db.Column(db.Text)
    family_id = db.Column(db.Integer,db.ForeignKey("family.id"))

    def __init__(self,surname,forename=None,middle_name=None):
        self.forename = forename
        self.middle_name = middle_name
        self.surname = surname
        self.family_id = db.relationship("family",backref="individual",lazy="dynamic")

    def __repr__(self):
        return f"""The individual is {self.forename} {self.middle_name}
        {self.surname}, their father is {self.family.father_id.forename}
        {self.family.father_id.middle_name} {self.family.father_id.surname}
        and their mother is {self.family.mother_id.forename}
        {self.family.mother_id.middle_name} {self.family.mother_id.surname}"""

db.create_all()

person1 = Individual("Bloggs", "David")
person2 = Individual("Bloggs", "Robert")
person3 = Individual("Smith", "Mary", "Ann")

db.session.add_all([person1,person2,person3])
db.session.commit()

print(person1)
print(person2)
print(person3)

任何帮助表示赞赏。谢谢。

Answer 1

有必要谈谈你的数据库设计中的一点

数据库需要家庭和个人之间的双重关系，因为创建个人需要一个家庭，在另一个地方，创建一个家庭需要一个母亲和父亲的身份。这是个问题。 一种设计方法是分配一个 familiy_id，每个人都有一个 family_id 和一个在家庭中的角色。

import os
from flask import Flask
from flask_sqlalchemy import SQLAlchemy
from flask_migrate import Migrate

basedir = os.path.abspath(os.path.dirname(__file__))

app = Flask(__name__)

app.config["SQLALCHEMY_DATABASE_URI"] = "sqlite:///"+os.path.join(basedir,"data.sqlite")
app.config["SQLALCHEMY_TRACK_MODIFICATIONS"] = False

db = SQLAlchemy(app)
Migrate(app, db)

class Family(db.Model):

    __tablename__ = "family"

    id = db.Column(db.Integer,primary_key=True)
    family_id = db.Column(db.Integer, unique=True)
    family_name = db.Column(db.Text)


    def __init__(self,family_id, family_name):
        self.family_id = family_id
        self.family_name = family_name


class Individual(db.Model):

    __tablename__ = "individual"

    id = db.Column(db.Integer, primary_key=True)
    forename = db.Column(db.Text)
    middle_name = db.Column(db.Text)
    surname = db.Column(db.Text)
    role = db.Column(
        db.Integer,
        nullable=False,
        server_default=db.text("'0'"),
        comment="Indicates whether is the role in the family . 2 = Father, 1= Mother, 0 = Other",
    )
    family_id = db.Column(db.Integer,db.ForeignKey("family.id"))

    def __init__(self, forename, middle_name, surname, family_id, role=0):
        self.forename = forename
        self.middle_name = middle_name
        self.surname = surname
        self.family_id = family_id
        self.role = role

   
db.create_all()

family = Family(1, "Kay Fam.")

son = Individual("John", "David", "Kay", 1)
father = Individual("Dave", "Luis", "Kay", 1, 2)

db.session.add(family)
db.session.add(son)
db.session.add(father)

db.session.commit()

新案例： 将个人分配给多个家庭/角色需要修改

 class Individual(db.Model):


    __tablename__ = "individual"

    id = db.Column(db.Integer, primary_key=True)
    individual_id = db.Column(db.Integer)
    forename = db.Column(db.Text)
    middle_name = db.Column(db.Text)
    surname = db.Column(db.Text)
    role = db.Column(
        db.Integer,
        nullable=False,
        server_default=db.text("'0'"),
        comment="Indicates whether is the role in the family . 2 = Father, 1= Mother, 0 = Other",
    )
    family_id = db.Column(db.Integer,db.ForeignKey("family.id"))

    def __init__(self, individual_id,  forename, middle_name, surname, family_id, role=0):
        self.individual_id = individual_id
        self.forename = forename
        self.middle_name = middle_name
        self.surname = surname
        self.family_id = family_id
        self.role = role

individual_id 很重要，为什么？因为不是唯一的，它是一个与个人相关的数字（id 表示 DB 上的位置，例如 individual_id == DNI） 这样就可以多次添加具有不同家庭/角色的个人。