使用sqlite3 for Python時如何在SQL中創建主鍵和外鍵？

Question

我嘗試創建兩個表，car_main 和 car_info。 car_main 有一個主鍵和一個外鍵，分別是 car_id 和 model_id。 car_info 有兩個外鍵，car_id 和 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

您的外鍵語句沒有意義，因為您引用的是同一張表

model_id INTEGER FOREIGN KEY REFERENCES car_main(car_id)

可能你需要

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)
);