m31

-- In all requests I change in names of tables and names of columns " " -> "_" (for example  Bet ID -> Bet_ID)

SELECT Player_ID, Bet_amount
FROM
    (SELECT Player_ID, Bet_amount, ROW_NUMBER() OVER (PARTITION BY Player_ID ORDER BY Bet_amount DESC) AS rk
    FROM
        (SELECT b.Player_ID, b.Bet_amount, p.Date
        FROM Bets_transactions AS b
        JOIN Periods AS p ON b.Date_ID=p.Date_ID
        WHERE p.Date = '2018-01-01') AS t1) AS t2
WHERE rk=2;