sqlite3外键根本不起作用

Question

    cur.execute("CREATE TABLE users(id integer PRIMARY KEY, username TEXT, password TEXT, email TEXT)")
    cur.execute("CREATE TABLE posts(id integer PRIMARY KEY, body TEXT, user_id int, FOREIGN KEY(user_id) REFERENCES users(id))")

I already enabled pragma foreign_keys = on, and it returned a 1. I created this database with python, and I used a database viewing program to check the fields. It showed everything correct from the primary keys, to the text fields, BUT no foreign key. It displays user_id as an int, nothing more. I also don't get any values put into it when making inserts. I feel that if I insert a user, than it should create a row, and be references in posts. But when I query the user_id field, it returns 'none'. What am I doing wrong?

edit:here is how I got it to work

@app.route('/add', methods=['POST'])
def add():       
    c = g.db.execute("INSERT INTO posts(body) VALUES(?)", [request.form['body']])
    b = g.db.execute("INSERT INTO users(username) VALUES(?)", [request.form['name']])
    get = g.db.execute("SELECT id from users where username=?", [request.form['name']])
    id = get.fetchone()  
    userid=str(id[0])
    bet = g.db.execute("SELECT id from posts where body=?", [request.form['body']])
    bid = bet.fetchone()
    postid = str(bid[0])
    e = g.db.execute("UPDATE posts SET user_id = (?) where id = (?)  ", [userid,postid])
    g.db.commit()
    flash('subbmited')
    return redirect(url_for('home'))

Answer 1

Foreign keys are used for managing relationships between records. However, in your code, you have not told the database that the two inserted records are related in any way.

You should insert the users record first so that you can use the newly inserted ID for the posts record:

def add():
    cursor = g.db.cursor()
    cursor.execute("INSERT INTO users(username) VALUES(?)", [request.form['name']])
    g.db.execute("INSERT INTO posts(body, user_id) VALUES(?,?)",
                 [request.form['body'], cursor.lastrowid])
    g.db.commit()
    ...

(Do you really want to create a new user for each post?)