pry output showing sqlite search problem

sqlite1.txt

[3] pry(main)> db.execute "select * from Users"
=> [["sanarothe2",
  "f82e77528ed1a1cc7fe33fcf751d90b11cd77d45",
  "3eec25493d63be0ad6fc3e196d9b0e472babddb7",
  "cccb6c91-c722-44cd-adce-51504e717bdb"],
 ["sanarothe",
  "6dc00946d373b7eeffff8b2a09535bd3105eb201",
  "0d01e5810b361c02731a8c178014ccbe86ca6f07",
  "b315763b-d234-4e2c-908a-7c403987785d"]]
[4] pry(main)> db.execute "select * from Users where Username=?", 'sanarothe'
=> []
[5] pry(main)> db.execute "select * from Users where Username=?", 'sanarothe2'
=> []
[6] pry(main)> db.execute "select * from Users where Username=?", "sanarothe"
=> []
[7] pry(main)> db.execute "select * from Users where Username=?", "sanarothe"
=> []

sqlite2.rb

def register_user(user_name, user_password, user_password_confirmation)
  db = SQLite3::Database.new("users.db")
  check_existing_user = db.prepare("SELECT * FROM Users WHERE Username = ?")
  user = check_existing_user.execute user_name
  user_exists_result = user.next # user.next will return nil if there are no more values to check out
  check_existing_user.close
  
  if user_password != user_password_confirmation
    return "01:PasswordMismatch"
  elsif user_exists_result == nil 
    salt = generate_salt
    hash = generate_hash(user_password, salt)
    uuid = generate_uuid
    insert_new_user_stmt = db.prepare "INSERT INTO Users VALUES (?, ?, ?, ?)"
    puts user_name
    puts hash
    puts salt
    puts uuid
    insert_new_user_stmt.execute user_name.chomp, hash, salt, uuid
    insert_new_user_stmt.close
    puts "01:RegisteredNewUser -- #{user_name}"
    return "01:RegisteredNewUser"
  else
    return "01:FoundUser"
  end

  db.close
end