В SQL базу не добавляется 0, если он стоит первым в строке

import sqlite3
import random
 
open_db = sqlite3.connect("card.s3db")
modify_db = open_db.cursor()
modify_db.execute("""CREATE TABLE IF NOT EXISTS card (  id INTEGER, 
                                                        number TEXT, 
                                                        pin TEXT, 
                                                        balance INTEGER DEFAULT 0   );""")
 
def open_n_read_db():
 
    modify_db.execute("SELECT id, pin FROM card")
    return {str(i[0]): i[1] for i in modify_db.fetchall()}
 
def write_to_db(account_number, full_card_number, pin, balance):
    
    modify_db.execute(f"INSERT into card VALUES ({account_number}, {full_card_number}, {pin}, {balance})")
    open_db.commit()
 
def creating_account(x):
 
    while True:
 
        issuer_identification_number = "400000"
        customer_account_number = "".join(random.choices([str(i) for i in range(1, 10)], k=9))
        pin = "".join(random.choices([str(i) for i in range(10)], k=4))
        
        if customer_account_number in x:
            continue
        else:
 
            number_to_check = issuer_identification_number + customer_account_number
            luhn1 = [int(number_to_check[i])*2 if i % 2 == 0 else int(number_to_check[i]) for i in range(15)]
            luhn2 = [i - 9 if i > 9 else i for i in luhn1]
 
            if int(str(sum(luhn2))[1]) != 0:
                checksum = str(10 - int(str(sum(luhn2))[1]))
            else:
                checksum = "0"
 
            card_number = issuer_identification_number + "".join(customer_account_number) + checksum
            write_to_db("".join(customer_account_number), card_number, pin, 0)
            break
    
    print("Your card has been created", "Your card number:", card_number, "Your card PIN:", pin, "", sep="\n")
 
def user_account():
    while True:
        print("1. Balance", "2. Log out", "0. Exit", sep="\n")
        user_choice = input()
        if user_choice == "1":
            print("\nBalance: 0\n")
            continue
        elif user_choice == "2":
            print("\nYou have successfully logged out!\n")
            return "log_out"
        elif user_choice == "0":
            print("\Bye!")
            return "exit"
 
def check_login(x):
    while True:
        print("\nEnter your card number:")
        user_input_card = input()
        print("Enter your PIN:")
        user_input_pin = input()
        if user_input_card[6:15] in x and x[user_input_card[6:15]] == user_input_pin:
            print("\nYou have successfully logged in!\n")
            return True
        else:
            print("\nWrong card number or PIN!\n")
            return False
 
while True:
    print("1. Create an account", "2. Log into account", "0. Exit", sep="\n")
    user_choice = input()
 
    if user_choice == "1":
        creating_account(open_n_read_db())
        continue
    elif user_choice == "2":
        if check_login(open_n_read_db()):
            if user_account() == "exit":
                print("Bye!")
                break
            else:
                continue
        else:
            continue
    elif user_choice == "0":
        print("Bye!")
        break

 '{pin}',