使用sqlite3 for Python时如何在SQL中创建主键和外键？

Question

I tried to create two tables, car_main, and car_info. car_main has a primary and foreign key, car_id and model_id, respectively. car_info has two foreign keys, car_id and model_id.

connection = sqlite3.connect("TutorialDB.db")
crsr = connection.cursor()
sql_command = """CREATE TABLE car_main (
car_id INTEGER PRIMARY KEY,
model_id INTEGER FOREIGN KEY REFERENCES car_main(car_id),
);"""
crsr.execute(sql_command)
sql_command = """CREATE TABLE car_info (
car_id INTEGER FOREIGN KEY REFERENCES car_main(car_id),
model_id INTEGER FOREIGN KEY REFERENCES car_main(model_id),
year INTEGER,
price INTEGER,
used BOOLEAN
);"""
crsr.execute(sql_command)
connection.close()```

Answer 1

Your foreign key statement makes no sense because you are referencing the same table

model_id INTEGER FOREIGN KEY REFERENCES car_main(car_id)

probably you need

CREATE TABLE car_info (
    model_id INTEGER PRIMARY KEY,
    year INTEGER,
    price INTEGER,
    used BOOLEAN
);

CREATE TABLE car_main (
    car_id INTEGER PRIMARY KEY,
    model_id INTEGER,
    FOREIGN KEY(model_id) REFERENCES car_info(model_id)
);