I have created a program in Tkinter in which users first have to choose whether s/he wants to sign in or sign up, I have completed the sign-up part of my application but having trouble with the sign-in part. I want to check if the user has already signed up or not when s/he will enter their details on the sign-up screen using python, Tkinter, and MySQL. I don't understand or have any idea how can I do that using MySQL-connector...

CodePudding user response：

Once you have a prepared-cursor object (I assume you have a cursor object, at least, since you have sign-up working?), you might issue a query such as this one:

cursor.execute(“SELECT COUNT(*) FROM users_table_name WHERE username=%s AND password_hash=%s”, (username_input, password_input)) # or whatever your authentication logic should be in the WHERE clause
result = cursor.fetchone()[0] # will be 1 if there is such a row, 0 if there is not

What this does:

• cursor.fetchone() returns a tuple containing as many comma-separated columns/values as you specified between SELECT and FROM--which in this case is just one value: the "count" of rows that match the condition in the WHERE clause (i.e., having the right username and password)
• Using a prepared cursor is critical, when user input will be a part of your query, in order to prevent SQL injection attacks. You want to avoid using any of the Python string-interpolation/string-building techniques to put the username or password the user entered into your query string, because this could allow the user to execute arbitrary SQL.

CodePudding user response：

if you want to build a simple query, check this w3school tutorial, you would just query the email to make sure the user is actually registered