python backend to check login

@app.route('/login', methods=['GET', 'POST'])
def login():
    if request.method == 'POST':
      userName = request.form["userName"]
      password = request.form["password"]
      data = checkAdmin(userName, password)
      global userCount
      if data:
        userCount+=1
        session["username"] = userName
        session['fullName'] = ""
        session['admin'] = "admin"
        return redirect('/')
      data = checkUser(userName, password)
      if data:
        userCount += 1
        session["username"] = userName
        session['fullName'] = data[0][5]
        return redirect('/')
      else:
        return render_template("login.html", error = "This user does not exist")
    else:
      print("in get")
      return render_template("login.html")



def checkUser(username, passwd):
  conn = sqlite3.connect("UserData.db")
  cursor = conn.cursor()
  
  selectQuery = f"SELECT * FROM registerData where userName =\"{username}\" AND password = \"{passwd }\""
  cursor.execute(selectQuery)
  data = cursor.fetchall()

  conn.close()

  return data


def checkAdmin(username, password):
    conn = sqlite3.connect("UserData.db")
    cursor = conn.cursor()
    cursor.execute(f"SELECT * FROM adminUsers where username=\'{username}\' and        password=\'{password}\'")
    data = cursor.fetchall()
    conn.close()
    return data