如何使 ON DELETE CASCADE 在 sqlite 3.7.4 中工作？

Question

我检查了几次功能列表，似乎级联应该可以工作。 当我执行这个 python 脚本时：

#!/usr/bin/env python3
import sqlite3

print(sqlite3.sqlite_version)

con = sqlite3.connect(':memory:')

a = "create table a (id integer primary key, name text)"
con.execute(a)

b = "create table b (id integer primary key, r integer, foreign key(r) references a(id) on delete cascade)"
con.execute(b)
con.commit()

a = "insert into a (name) values (\"abc\")"
con.execute(a)
con.commit()

print(con.execute("select * from a").fetchall())

a = "insert into b (r) values (1)"
con.execute(a)
con.commit()

print(con.execute("select * from b").fetchall())

a = "delete from a where id=1"
con.execute(a)
con.commit()

print(con.execute("select * from b").fetchall())
print(con.execute("select * from a").fetchall())

我得到了这些结果：

3.7.4
[(1, 'abc')]
[(1, 1)]
[(1, 1)]
[]

这证明级联没有发生。我做错了什么或获得与级联相同结果的解决方案是什么？

Answer 1

出于兼容性目的，禁用 SQLite 外键。您需要在每次连接到数据库后立即手动启用它们。

con.execute("PRAGMA foreign_keys = ON")

Answer 2

用户Thibault J 在这个问题上有一个更好的答案：Enable integrity checking with sqlite in django 说：

from django.db.backends.signals import connection_created
def activate_foreign_keys(sender, connection, **kwargs):
    """Enable integrity constraint with sqlite."""
    if connection.vendor == 'sqlite':
        cursor = connection.cursor()
        cursor.execute('PRAGMA foreign_keys = ON;')

connection_created.connect(activate_foreign_keys)