Below code does not check for the existing username

Question

I am trying to register a user. I am having problem in preventing the user to register if the username typed already exists in the database.

@app.route("/register", methods=["GET", "POST"])
def register():
    """Register user"""

    if request.method == "GET":
        return render_template("register.html")

    elif request.method == "POST":

        # Ensure username was submitted
        if not request.form.get("username"):
            return apology("must provide username", 400)

        # Ensure password was submitted
        elif not request.form.get("password"):
            return apology("must provide password", 400)

        # Ensure password confirmation was submitted
        elif not request.form.get("password-confirmation"):
            return apology("must provide password confirmation", 400)

        # Check if the password confirmation field matches the password field
        elif request.form.get("password-confirmation") != request.form.get("password"):
            return apology("Your passwords didn't match", 400)

        # Query database for that username
        row = db.execute("SELECT * FROM users WHERE username = ?", request.form.get("username"))

        # Database
        database = db.execute("SELECT * FROM users")

        # Ensure username is not already in the database
        if row in database:
            return apology("username already exists", 400)

        # Insert username and password into the database AND Hash user's password
        insert = db.execute("INSERT INTO users (username,hash) VALUES(?,?)" , request.form.get("username"), generate_password_hash(request.form.get("password")))

        # Remember which user has logged in
        session["user_id"] = insert

        # Redirect user to home page
        return redirect("/")

Instead of getting "username already exists", I get "internal server error".

Can someone please specify why it might be the case.?

`db.execute` likely requires an iterable containing the username to search for, not just the username itself, as an argument. `row = db.execute("SELECT * FROM users WHERE username = ?", (request.form.get("username"),))` — chepner, Jul 25 '21 at 18:11
Hello @chepner, Can you please elaborate a bit on your above comment.? Awaiting your kind response — Khan, Jul 26 '21 at 11:37
Read the documentation for whatever database library you are using. — chepner, Jul 26 '21 at 12:41

score 0 · Answer 1 · answered Jul 25 '21 at 18:12

0

Your SELECT syntax is wrong. It should be rows = db.execute("SELECT * FROM users WHERE username = :username", username=request.form.get("username"))

answered Jul 25 '21 at 18:12

haidousm

556
6
21

Are ":username" and "?" not the same things.? Both are placeholders, right.? – Khan Jul 25 '21 at 19:23

DinoCoderSaurus · Answer 2 · 2021-07-27T11:49:46.057

0

This if row in database: will never be true.

row is a list, so it is trying to find a list in database. database is itself a list, but does not contain any lists, only dictionaries.

Program would know if username is already in users if row is not the empty list. Hint, Hint.

edited Jul 27 '21 at 11:49

answered Jul 27 '21 at 11:29

DinoCoderSaurus

6,110
2
10
15

Below code does not check for the existing username

2 Answers2