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Mysql – why my else cannoot execute while the statement is else?

I want to create a login page script with the username and password as the data account from db. n then when my input is doesn’t match the else didn’t execute while username and password is did not exist in db. so what should i do to fix this. any somebody help me please

def logindb():
print ("=="*15+"nPlease insert your username and password.")
username = input ("Username : ")
password = input ("Password : ")
cursor.execute(f"SELECT * FROM data WHERE username='{username}' and password='{password}'")
result = cursor.fetchall()
for i in result:
    if (i[0]) == username and (i[1]) == password:
        print ("=="*15+"ntLogin Success.n"+"=="*15)
    else:
        print ("=="*15+"nUsername or password is wrong.n"+"=="*15)
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3

Answers


  1. 0

    Try changing:

    cursor.execute(f"SELECT * FROM data WHERE username='{username}' and password='{password}'")

    To:

    cursor.execute(f"SELECT username, password FROM data WHERE username='{username}' and password='{password}'")

    You’re selecting ALL* columns, and if your 0 index column is not username, and your 1 index column is not password, your query result will not match up your submitted username and password.

    if (i[0]) == username and (i[1]) == password:

    It’s also not a good idea to run your SELECT statements wide open if you don’t need to. Retrieve only the columns explicitly that you need to retrieve.

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  2. 0

    You should really use a parameterized query.

    But if you are going to use this method of data retrieval then I would go one step further then Griv’s answer

    cursor.execute(f"SELECT userid FROM data WHERE username='{username}' and password='{password}'")

    I would never fetch the username or password. Instead, check for its existence by fetching the primary key of the table.

    Then check if that value is null or not.

    I am not familiar with python, I assume the f"SELECT is not a typo

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  3. 0

    In your code snippet, the statement can NEVER be else!

    You query for a database entries matching username and password. For every entry (with the matching username and password) you again check if these credentials are correct.

    I guess what you want, is to check if there are records found.

    Something like this:

    result = cursor.fetchall()
if (len(result) > 0):
    print ("=="*15+"ntLogin Success.n"+"=="*15)
else:
    print ("=="*15+"nUsername or password is wrong.n"+"=="*15)

    Side note: you really should hash the password instead of saving it as plain text in the database.

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