Hacker Rank - User Transactions Count

-- problem statement -> https://imgur.com/a/hcLd5Ns

SELECT
    u.user_name,
    SUM(CASE WHEN t.transaction_id LIKE '19%' THEN 1 ELSE 0 END) AS transactions_2019,
    SUM(CASE WHEN t.transaction_id LIKE '20%' THEN 1 ELSE 0 END) AS transactions_2020,
    SUM(CASE WHEN t.transaction_id LIKE '21%' THEN 1 ELSE 0 END) AS transactions_2021
FROM
    USERS u,
    TRANSACTIONS t
WHERE
    u.user_id = t.user_id
GROUP BY
    u.user_id;