Comparing user input to usernames in database - mysql

Question

I am having an issue with comparing user input to a database of already used usernames. The database is working exactly how it is supposed to, but what seems like a simple task it proving to be more difficult than I thought. I figure I am missing something really simple! I get no error codes from the code but it does not print "username is taken" when the username is in fact in the database.
Thus far I have tried a for loop to compare the user's input to the database, I have tried making a list of the usernames in the database and iterating through the list to compare the user input:
### check to see if the user is already in the database
import mysql.connector
# Database entry
mydb = mysql.connector.connect(
host='Localhost',
port='3306',
user='root',
passwd='passwd',#changed for help
database='pylogin'
)
searchdb = 'SELECT username FROM userpass'
mycursor = mydb.cursor()
mycursor.execute(searchdb)
username = mycursor.fetchall()
print(username)
user = input('username')
for i in username:
if user == username:
print('username is taken')
else:
print("did not work")
Output that does not work:
[('Nate',), ('test',), ('test1',), ('test2',), ('n',), ('test4',)] username: n
('Nate',)
('test',)
('test1',)
('test2',)
('n',)
('test4',)
I expect the above code to iterate through each database entry and compare it to the user's input to verify that the username is not already taken. It should print "username is taken" instead it prints "did not work".

Answer 1

Welcome to Stack Overflow Nate!
You can use:
mycursor.execute("SELECT * FROM userpass WHERE username = ?", [(user)])
results = cursor.fetchall()
To create a variable called 'results' that stores all (*) of the column values for the record in the userpass database table where the username of the record is equal to the value of the user variable.
You can then use an if statement:
if results:
That is run if the results variable has a value (if there is a record with a username that is equal to the value of the user variable in the table) AKA if the username is taken.
This if statement can then, when run print 'username is taken'
The full code:
import mysql.connector
# Database entry
mydb = mysql.connector.connect(
host='Localhost',
port='3306',
user='root',
passwd='passwd',#changed for help
database='pylogin'
)
user = input('username')
mycursor.execute("SELECT * FROM userpass WHERE username = ?", [(user)])
results = cursor.fetchall()
if results:
print('username is taken')
else:
print("did not work")

Answer 2

edit* when adding this code the the rest of the program and testing i found it gives the results username taken every time, even if it is a new username. If you have any recommendations to fix this, I am open to them. I am going to continue work on this and will post results when the program is working properly.
I would like to thank you guys for your help, I did find the response I was looking for!
### check to see if user is already in database
import mysql.connector
# Database entry
mydb = mysql.connector.connect(
host='Localhost',
port='3306',
user='root',
passwd='passwd',#changed for help
database='pylogin'
)
mycursor = mydb.cursor()
user = input('username')
mycursor.execute('SELECT * FROM userpass WHERE username = username')
results = mycursor.fetchall()
if results:
print('Username is taken')
else:
print('did not work')`